JP2010251612A - Nitride semiconductor light emitting device manufacturing method, light emitting device, nitride semiconductor light emitting layer, and nitride semiconductor light emitting device - Google Patents

Abstract

In a nitride semiconductor light emitting device having an emission wavelength of 430 nm or more, the light emission efficiency is improved, the yield is improved, or the life of the light emitting device is extended.
The light emitting layer includes one or more well layers, one or more barrier layers, and one or more protective layers provided between and in contact with the well layers and the barrier layers. And a step of forming a well layer with a group III element material containing In and Ga, a carrier gas containing ammonia gas and nitrogen, and a group III element material containing Ga, ammonia gas and a carrier containing nitrogen A step of forming a protective layer with a gas; and stopping supply of the Group III element material containing Ga, supplying ammonia gas and a carrier gas containing nitrogen and hydrogen, and interrupting crystal growth for a predetermined time. And a step of forming a barrier layer with the group III element raw material containing Ga, ammonia gas, and a carrier gas containing nitrogen and hydrogen in this order.
[Selection] Figure 9

Description

  The present invention relates to a method for manufacturing a nitride semiconductor light emitting element, a light emitting device, a nitride semiconductor light emitting layer, and a nitride semiconductor light emitting element.

  In manufacturing a nitride semiconductor light emitting device using an InGaN material or the like, as a manufacturing method for further increasing the light emission intensity of the obtained light emitting device, for example, in Patent Document 1, an active layer (light emitting layer) having a quantum well structure is used. By providing a manufacturing method in which a predetermined growth interruption time is provided during the vapor phase crystal growth and a suitable amount of hydrogen gas is introduced at an appropriate introduction timing during the growth interruption, the emission intensity of the obtained light emitting element can be increased. Is disclosed.

  In Patent Document 2, in order to prevent decomposition of In in the well layer that occurs when the temperature is raised to grow the barrier layer after growing the well layer, the well layer and barrier of the active layer are prevented. It is disclosed that an intermediate layer having a larger band gap energy than the barrier layer is formed between the layers. Furthermore, paragraph 0041 of Patent Document 2 discloses that the driving voltage of the element can be reduced by forming a network structure in which the surface of the intermediate layer has a plurality of regions recessed or penetrated by the temperature raising step. Has been.

JP 2003-289156 A JP 2001-168471 A

  However, even if the manufacturing method of the light emitting layer disclosed in Patent Document 1 is used, the light emitting efficiency of the obtained light emitting element is not sufficient, and there is a problem that the emission wavelength fluctuates greatly. Moreover, even if the form of the light emitting layer disclosed in Patent Document 2 is used, the light emitting efficiency of the obtained light emitting element is not sufficient.

  Generally, in order to obtain a nitride semiconductor light emitting device having an emission wavelength of 430 nm or more, the In composition ratio of the InGaN well layer in the light emitting layer having the quantum well structure is set to be relatively high. This is because the energy band gap of the InGaN well layer decreases as the In composition ratio increases, and the emission wavelength increases accordingly.

  In order to grow an InGaN well layer having a high In composition ratio, it is necessary to supply a large amount of source gas containing In in the vapor phase growth process. In such a situation, a high concentration of In is contained in the gas phase, and In that could not be taken into the solid phase (well layer) tends to segregate on the surface. The In segregation region tends to be a non-light-emitting region, and the light emission efficiency of the light-emitting layer is significantly reduced.

  In fact, according to the results of experiments conducted by the present inventors, in a light emitting device having an emission wavelength of 430 nm or more, a non-light emitting region that seems to be caused by In segregation was observed using a fluorescence microscope. In addition, these non-light-emitting regions are composed of a p-type nitride semiconductor layer (in particular, the p-type nitride semiconductor layer referred to here is one or more layers after the light-emitting layer is grown, and all of the layers are p-type). The light emitting layer has a temperature of 900 ° C. or more and 1200 ° C. or less until the completion of the growth of the layer. When exposed to temperature for at least 3 minutes or more (not limited to the crystal growth period, but also includes a period during which the temperature is simply raised and lowered), there was a tendency to appear prominently.

  That is, deterioration of the well layer having a high In composition ratio can proceed due to the thermal history of the light emitting layer. It is assumed that all the steps exposed to the temperature of 900 ° C. or higher and 1200 ° C. or lower for at least 3 minutes are steps in which a p-type nitride semiconductor layer is laminated on the light emitting layer, and the p-type nitride semiconductor layer is In consideration of the general growth rate, the thickness of the p-type nitride semiconductor layer corresponds to 0.35 μm or more. Specifically, examples of the p-type nitride semiconductor layer requiring a temperature of 900 ° C. or higher and 1200 ° C. or lower include an AlGaN layer and / or a GaN layer. That is, the non-light-emitting region (or In segregation) tends to appear remarkably in the laser element among the light-emitting elements.

  In particular, the surface of the well layer is exposed when the intermediate layer on the well layer has a network structure having a plurality of depressed or penetrated regions as described in Japanese Patent Laid-Open No. 2001-168471 (Patent Document 2). Therefore, In segregation and fluctuations in the In composition ratio are induced to promote the deterioration of the well layer.

  Therefore, the present invention provides a nitride semiconductor light emitting device having an emission wavelength of 430 nm or more, and the non-semission caused by In segregation or excess In concentration in the light emitting layer while keeping the interface of the light emitting layer (particularly the well layer) as flat as possible. An object is to improve the light emission efficiency, the yield, or the lifetime of the light emitting element by suppressing the generation of the light emitting region.

The present invention relates to a nitride semiconductor light emitting device including an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light emitting layer formed between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer. A manufacturing method comprising:
The light emitting layer is made of one or more well layers made of a nitride semiconductor, one or more barrier layers made of a nitride semiconductor, and a nitride semiconductor provided in contact with the well layer and the barrier layer. Including one or more protective layers and having an emission wavelength of 430 nm or more,
A well layer forming step of forming a well layer by supplying a group III element source material containing In and Ga, ammonia gas, and a carrier gas containing nitrogen;
A protective layer forming step of forming a protective layer by supplying a Group III element source material containing Ga, ammonia gas, and a carrier gas containing nitrogen; and
A first growth interruption step of stopping the crystal growth for a predetermined time by stopping supply of the Group III element material containing Ga and supplying a carrier gas containing ammonia gas and nitrogen and hydrogen;
A nitride semiconductor light emitting device comprising: a group III element source material containing Ga, ammonia gas, and a barrier layer forming step for supplying the carrier gas containing nitrogen and hydrogen to form the barrier layer in this order. It is a manufacturing method of an element.

  The protective layer is preferably provided in contact with the well layer on the p-type nitride semiconductor layer side.

  The protective layer is composed of one or more nitride semiconductor layers, and at least the layer in direct contact with the well layer is preferably a nitride semiconductor layer not containing In.

  After the formation of the light emitting layer, the light emitting layer is preferably exposed to a temperature of 900 ° C. or higher and 1200 ° C. or lower for 3 minutes or more.

The thickness of the p-type nitride semiconductor layer is preferably 0.35 μm or more and 1 μm or less.
The thickness of the protective layer is preferably 0.25 nm or more and 1.2 nm or less.

The thickness of the well layer is preferably 1 nm or more and 3.2 nm or less.
The barrier layer preferably has a thickness of 15 nm to 35 nm.

The protective layer preferably includes a GaN layer and / or an AlGaN layer.
The present invention also relates to a method for manufacturing the nitride semiconductor light emitting device, wherein the well layer is an InGaN layer or an AlInGaN layer.

  The barrier layer preferably includes at least one layer selected from the group consisting of an InGaN layer, a GaN layer, an AlGaN layer, and an InAlGaN layer.

  It is preferable that the flow rate of ammonia gas in the protective layer forming step is equal to or higher than the flow rate of ammonia gas in the well layer forming step.

  The carrier gas used in the protective layer forming step further contains hydrogen in addition to nitrogen, and the proportion of hydrogen in the carrier gas is preferably 1 mol% or more and 20 mol% or less.

  It is preferable that the ratio of hydrogen in the carrier gas in the first growth interruption step is 1 mol% or more and 35 mol% or less with respect to the flow rate of ammonia gas in the protective layer forming step.

  The proportion of hydrogen in the carrier gas used in the barrier layer forming step is preferably 1 mol% or more and 20 mol% or less.

  Between the first growth interruption step and the barrier layer formation step, the supply of the group III element raw material is stopped, and a carrier gas consisting of ammonia gas and nitrogen is supplied for a predetermined time. It is preferable to further include a second growth interruption step for interrupting the growth.

  Between the first growth interrupting step and the barrier layer forming step, the supply of the group III element raw material is stopped, and an ammonia gas and a carrier gas composed of hydrogen and nitrogen are supplied for a predetermined time, It is preferable to further include a third growth interruption step for interrupting crystal growth.

  Between the second growth interruption step and the barrier layer formation step, the supply of the group III element raw material is stopped, and a carrier gas composed of hydrogen and nitrogen is supplied together with the ammonia gas for a predetermined time. It is preferable to further include a third growth interruption step for interrupting the growth.

  The present invention also relates to a light-emitting device including the nitride semiconductor light-emitting element manufactured using the nitride semiconductor light-emitting element manufacturing method.

  Furthermore, the present invention is a nitride semiconductor light emitting layer formed on a surface of a substrate, and is provided in contact with one or more well layers, one or more barrier layers, and the well layers and the barrier layers. The interface between the main surface of the well layer on the substrate side and the barrier layer is substantially flat, and the other main surface of the well layer is covered with the protective layer. Further, the present invention also relates to a nitride semiconductor light emitting layer characterized in that the cross-sectional shape of the interface where the other main surface of the well layer is in contact with the protective layer is a wave shape.

  The protective layer is composed of one or more nitride semiconductor layers, and at least the layer in direct contact with the well layer is preferably a nitride semiconductor layer not containing In.

  The present invention also relates to a nitride semiconductor light emitting device including the nitride semiconductor light emitting layer.

  According to the present invention, in a nitride semiconductor light emitting device having an emission wavelength of 430 nm or more, it is possible to suppress the generation of a non-light emitting region while maintaining the flatness of the interface of the well layer as much as possible, thereby improving the light emission efficiency ( (Suppression of non-light emission spots) and longer life of the laser element (reduction of internal loss due to improvement in interface flatness) can be obtained.

  Further, the improvement of the light emission efficiency can contribute to the reduction of power consumption of various devices using the light emitting element.

FIG. 3 is a schematic cross-sectional view showing a stacked structure of the nitride semiconductor light emitting element of Embodiment 1. FIG. 3 is a schematic cross-sectional view illustrating an example of a well layer forming process according to the first embodiment. 3 is a schematic cross-sectional view showing an example of a protective layer forming step of Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view showing an example of a first growth interruption process of Embodiment 1. FIG. 3 is a schematic cross-sectional view showing an example of a barrier layer forming process of Embodiment 1. FIG. 6 is a schematic cross-sectional view showing an example of a second growth interruption process of the first embodiment. FIG. 6 is a schematic cross-sectional view showing an example of a third growth interruption process of the first embodiment. 3 is a schematic cross-sectional view illustrating the nitride semiconductor light-emitting element of Example 1. FIG. It is typical sectional drawing which shows an example of the nitride semiconductor light emitting layer formed with the manufacturing method of this invention. It is typical sectional drawing which shows an example of the nitride semiconductor light emitting layer which does not have the protective layer formed by the conventional manufacturing method.

  In the following, various embodiments of the present invention will be described with reference to the drawings. In the drawings of the present application, the length, width, thickness, and the like are changed as appropriate for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships. In particular, the thickness is shown relatively appropriately enlarged. In the drawings, the same reference numerals represent the same or corresponding parts.

<Embodiment 1>
In the schematic cross-sectional view of FIG. 1, the laminated structure of the nitride semiconductor light emitting device 10 manufactured in Embodiment 1 of the present invention is illustrated. As shown in FIG. 1, the nitride semiconductor light emitting device 10 of this embodiment includes a substrate 11, an n-type nitride semiconductor layer 12, a light emitting layer 13, and a p-type nitride semiconductor layer 14.

As the substrate 11 used in this embodiment, sapphire, GaN (gallium nitride), AlN (aluminum nitride), AlGaN (aluminum gallium nitride), GaAs (gallium arsenide), Si, SiC (silicon carbide), or ZrB ₂ ( A base material itself such as zirconium diboride) or a nitride semiconductor layer crystal-grown on the base material can be used. The principal plane orientation of the substrate 11 is (0001) plane, (11-20) plane or (1-100) plane of nonpolar plane, or (1-102) semipolar plane of hexagonal substrate. The (001) plane or the (111) plane can be used for a cubic substrate.

  The n-type nitride semiconductor layer 12 is composed of one or more nitride semiconductor layers, and as a material constituting each nitride semiconductor layer, for example, GaN containing n-type impurities such as Si, AlGaN, InAlGaN, or InGaN Can be used. However, all the layers constituting the n-type nitride semiconductor layer 12 do not need to contain an n-type impurity, and an undoped layer may be included in a part of the n-type nitride semiconductor layer 12. When a nitride semiconductor laser device is manufactured as a nitride semiconductor light emitting device, the layer directly in contact with the light emitting layer 13 among the nitride semiconductor layers constituting the n type nitride semiconductor layer 12 contains n type impurities such as Si. It is preferable that it is an undoped layer which does not contain. This is to prevent light absorption by the dopant.

  The light emitting layer 13 includes one or more well layers made of a nitride semiconductor, one or more barrier layers made of a nitride semiconductor, and one or more protective layers provided in contact with the well layer and the barrier layer. Has been. Here, the protective layer is preferably provided in contact with the well layer on the p-type nitride semiconductor layer side. The light emitting layer 13 may have a single or multiple quantum well structure. In a multiple quantum well structure, the stacking of the well layer and the barrier layer may be repeated starting from the barrier layer and terminated by the barrier layer, or the stacking of the barrier layer and the well layer may be repeated starting from the well layer. You may end. The light emitting layer 13 will be described in more detail later.

  The method for producing a nitride semiconductor light emitting device of the present invention is suitably used for a light emitting device including the light emitting layer 13 having an emission wavelength of 430 nm or more. This is because in the light emitting layer 13 having an emission wavelength of less than 430 nm, the In concentration is low and In segregation does not become a problem. Furthermore, the emission wavelength of the light emitting layer 13 is more preferably 580 nm or less. In order for the emission wavelength to exceed 580 nm, a high concentration of In is required. In this case, the crystal quality of the light emitting layer 13 is significantly lowered and becomes impractical.

  The p-type nitride semiconductor layer 14 is composed of one or more nitride semiconductor layers, and GaN, AlGaN, InAlGaN, or InGaN containing p-type impurities such as Mg is used as a material constituting each nitride semiconductor layer. Can do. However, all the layers constituting the p-type nitride semiconductor layer 14 do not need to contain p-type impurities, and an undoped layer may be included in a part of the p-type nitride semiconductor layer 14. When a nitride semiconductor laser device is manufactured as a nitride semiconductor light emitting device, a layer directly in contact with the light emitting layer 13 among the nitride semiconductor layers constituting the p type nitride semiconductor layer 14 contains p-type impurities such as Mg. The undoped layer is preferably not included.

(Manufacture of nitride semiconductor light emitting devices)
Next, an example of a method for manufacturing the nitride semiconductor light emitting device 10 as shown in FIG. 1 will be described. First, the substrate 11 is placed in an MOCVD (metal organic vapor phase deposition) apparatus and maintained at a temperature suitable for crystal growth of the n-type nitride semiconductor layer 12. Then, using a carrier gas containing nitrogen gas and hydrogen gas, a source gas containing a group III element, a doping gas containing Si, and an ammonia gas are introduced into the MOCVD apparatus, and one or more n-type nitridings are formed on the substrate 11. The physical semiconductor layer 12 is crystal-grown.

  Here, when a part of the one or more n-type nitride semiconductor layers 12 is made of GaN or AlGaN, the substrate temperature for crystal growth is preferably 900 ° C. or higher and 1200 ° C. or lower, and 1000 ° C. or higher. It is more preferable that the temperature is 1100 ° C. or lower. When a part of one or more n-type nitride semiconductor layers 12 is made of InAlGaN, the substrate temperature is preferably 700 ° C. or higher and 1000 ° C. or lower. Further, when a part of the one or more n-type nitride semiconductor layers 12 is made of InGaN, the substrate temperature is preferably 700 ° C. or higher and 900 ° C. or lower. That is, it is preferable that the n-type nitride semiconductor layer 12 is crystal-grown within a suitable substrate temperature range because the crystallinity of the n-type nitride semiconductor layer 12 is improved.

As the raw material gas containing a Group III element, for example, _{TMG ((CH 3) 3 Ga} : _{trimethylgallium), TEG ((C 2 H} 5) 3 Ga: triethyl _{gallium), TMA ((CH 3)} 3 Al: Trimethylaluminum), TEA ((C ₂ H ₅ ) ₃ Al: triethylaluminum), TMI ((CH ₃ ) ₃ In: trimethylindium), TEI ((C ₂ H ₅ ) ₃ In: triethylindium), etc. are used. be able to. As the doping gas containing Si, may be used, for example SiH ₄ (silane) gas or the like. Also, monomethyl hydrazine or dimethyl hydrazine can be used instead of ammonia gas.

  The substrate temperature suitable for crystal growth of the light emitting layer 13 on the one or more n-type nitride semiconductor layers 12 is that the light emitting layer 13 (the light emitting layer is composed of a well layer, a barrier layer, and a protective layer) is partially InGaN. When it consists of, it is preferable that it is 600 to 900 degreeC. When a part of the light emitting layer 13 is made of GaN, the substrate temperature is preferably 700 ° C. or higher and 1080 ° C. or lower, and more preferably 750 ° C. or higher and 1000 ° C. or lower. When a part of the light emitting layer 13 is made of InAlGaN or AlGaN, the substrate temperature is preferably 700 ° C. or higher and 1000 ° C. or lower. When the light emitting layer 13 is crystal-grown within these substrate temperature ranges, the light emitting layer 13 can have good light emission characteristics. Note that the same kind of gas as in the case of the n-type nitride semiconductor layer 12 can be used as the source gas containing the group III element and the ammonia gas used in the formation of the light emitting layer 13. In addition, when Si is added to the light emitting layer 13, a doping gas containing Si may be introduced into the MOCVD apparatus.

  After the formation of the light emitting layer 13, a source gas containing a group III element, a doping gas containing Mg and an ammonia gas are introduced into the MOCVD apparatus using a carrier gas containing nitrogen gas and hydrogen gas. A crystal is grown to form a p-type nitride semiconductor layer 14. Here, the substrate temperature suitable for forming the p-type nitride semiconductor layer 14 is as follows. When a part of the p-type nitride semiconductor layer 14 is made of GaN or AlGaN, the temperature is preferably 900 ° C. or higher and 1200 ° C. or lower, and more preferably 1000 ° C. or higher and 1100 ° C. or lower. When a part of the p-type nitride semiconductor layer 14 is made of InAlGaN, the substrate temperature is preferably 700 ° C. or higher and 1000 ° C. or lower. Furthermore, when a part of the p-type nitride semiconductor layer 14 is made of InGaN, the substrate temperature is preferably 700 ° C. or higher and 900 ° C. or lower. That is, when the p-type nitride semiconductor layer 14 is crystal-grown within a suitable substrate temperature range, the crystallinity of the p-type nitride semiconductor layer 14 is improved.

Here, as the doping gas containing Mg, for example, Cp ₂ Mg (cyclopentadienyl magnesium) or (EtCp) ₂ Mg (bisethylcyclopentadienyl magnesium) can be used. Since (EtCp) ₂ Mg is a liquid at normal temperature and pressure, the response when the amount introduced into the MOCVD apparatus is changed is better than Cp ₂ Mg which is solid under the conditions, It is easy to keep the vapor pressure constant. In this case, it is possible to easily suppress the introduction amount of the doping gas containing Mg from fluctuating for each production lot. In addition, as the source gas containing group III element and ammonia gas used in the formation of the p-type nitride semiconductor layer 14, the same kind of gas as in the case of the n-type nitride semiconductor layer 12 and the light emitting layer 13 is used. it can.

  In all the steps in which the layers constituting the p-type nitride semiconductor layer 14 are stacked between the growth of the light-emitting layer 13 and the completion of the growth of the p-type nitride semiconductor layer 14, the light-emitting layer 13 is 900 ° C. or higher. If it is exposed to a temperature of 1200 ° C. or lower for at least 3 minutes, the thickness becomes 0.35 μm or more in consideration of the growth rate of a general p-type nitride semiconductor layer 14.

  More specifically, the p-type nitride semiconductor layer requiring a temperature of 900 ° C. or higher and 1200 ° C. or lower is a layer mainly composed of an AlGaN layer and / or a GaN layer. For example, in the case of a laser element, a high-quality GaN light guide layer, an AlGaN cladding layer, a GaN contact layer, and the like are required as a part of the p-type nitride semiconductor layer 14, and these layers are 900 ° C. or higher and 1200 ° C. It is desirable that the film be formed at a temperature of ℃ or less.

  The thickness of the p-type nitride semiconductor layer 14 is preferably 1 μm or less. If the thickness of the p-type nitride semiconductor layer 14 exceeds 1 μm, the light emitting layer is exposed to heat at a high temperature for a long time, and there is a concern that the non-light emitting region may increase due to thermal degradation of the light emitting layer. .

(Formation of light emitting layer)
Below, the formation method of a light emitting layer is demonstrated in detail among the manufacturing methods of the nitride semiconductor light emitting element of this embodiment. The light emitting layer forming method in this embodiment includes a well layer forming step for forming an InGaN well layer, a protective layer forming step for forming a GaN protective layer, a first growth interruption step, and a barrier layer made of a nitride semiconductor. A barrier layer forming step to be formed is included. The schematic cross-sectional views of FIGS. 2 to 5 illustrate each step of the method for forming the light emitting layer 13 in the present embodiment.

  The nitride semiconductor light emitting layer of the present invention includes one or more well layers, one or more barrier layers, and one or more protective layers provided in contact with each other between the well layers and the barrier layers. The interface between the main surface on the side and the barrier layer is substantially flat, the other main surface of the well layer is covered with a protective layer, and the interface between the other main surface of the well layer and the protective layer is in contact The cross-sectional shape is a wave shape. In such a wave shape, it is preferable that the wave periods are all 150 nm or more and the wave height difference is 30% or less of the average value of the average maximum thickness of the well layers. Since one interface is not completely flat, it is possible to prevent a decrease in the output of the light emitting diode during high current injection. However, exceeding the above range is not preferable because the injected carriers are scattered at the interface and the loss inside the light emitting element increases.

  In the present invention, Si can be added to at least one of the well layer, the barrier layer, and the protective layer. When a nitride semiconductor laser device is manufactured as the nitride semiconductor light emitting device, it is preferable that all layers of the well layer, the barrier layer, and the protective layer are undoped.

(Well layer formation process)
As shown in FIG. 2, the well layer 13 a is stacked on the n-type nitride semiconductor layer 12 in the well layer forming step.

  In the present embodiment, one or more such well layers 13 a are formed in the light emitting layer 13. When obtaining the light emitting layer 13 having an emission wavelength of about 450 nm, it is preferable to form two or three well layers 13a. When obtaining the light emitting layer 13 having an emission wavelength of about 470 nm, three to five layers are formed. It is preferable to form the well layer 13a. Moreover, when obtaining the light emitting layer 13 with an emission wavelength of 500 nm or more, it is preferable to form the well layer 13a having 5 layers or more and 10 layers or less. This enables laser oscillation.

  The thickness of the well layer 13a is preferably 1 nm or more and 3.2 nm or less from the viewpoint of effectively suppressing the non-light emitting region. As the well layer 13a becomes thicker, it becomes easier for excess In to accumulate on the surface of the well layer. Therefore, if the thickness of the well layer 13a exceeds 3.2 nm, excess In causing the non-light emission will be reduced later. It tends to be difficult to remove in the first growth interruption step.

  In the present invention, the well layer 13a is preferably an InGaN layer or an AlInGaN layer. When manufacturing a nitride semiconductor laser device as the nitride semiconductor light emitting device, the well layer 13a is preferably an InGaN layer. Of the one or more layers constituting the n-type nitride semiconductor layer 12, the layer in contact with the well layer 13a (InGaN layer) is preferably composed of an undoped InGaN layer, and among the group III elements in the undoped InGaN layer, The In composition ratio is 2 mol% or more and 10 mol% or less, and the thickness of the well layer 13a including the undoped InGaN layer is preferably 25 nm or more and 150 nm or less. This is a condition for forming a stable well layer for obtaining an emission wavelength of 430 nm or more.

  When forming the InGaN well layer 13a on the n-type nitride semiconductor layer 12, the substrate temperature is maintained at a temperature suitable for crystal growth of the InGaN well layer 13a, and a group III element source material 101 containing In and Ga. A carrier gas 103 containing ammonia gas 102 and nitrogen is introduced into the MOCVD apparatus (see FIG. 2).

  Here, a temperature suitable for crystal growth of the InGaN well layer 13a is 600 ° C. or higher and 850 ° C. or lower. The reason why the growth temperature of the InGaN well layer 13a is set lower than the growth temperature suitable for the n-type InGaN layer 12 described above is that a high In composition ratio is required in order to form the InGaN well layer 13a having an emission wavelength of 430 nm or more. This is because (at least 7 mol% or more in the group III element) is necessary.

  In order to obtain a high In composition ratio, in addition to a relatively low crystal growth temperature, it is necessary to increase the supply amount of the group III element material containing In. In an InGaN well layer 13a grown under such conditions using a conventional manufacturing method, a large amount of excess In that could not be incorporated tends to remain on the surface, and non-segregation due to In segregation. This tends to result in an increase in the light emitting area. This non-light-emitting region deteriorates the characteristics of the light-emitting element.

  When the well layer 13a is made of InGaN, the carrier gas 103 containing nitrogen is preferably a carrier gas made only of nitrogen. According to the experiments by the present inventors, when a carrier gas containing nitrogen and hydrogen is used to form a well layer made of InGaN, the effect of suppressing the non-light emitting region of the resulting well layer (the effect of suppressing In segregation) is somewhat Although recognized, the effect of shortening the emission wavelength was remarkably great, and in some cases, an emission wavelength of 430 nm or more could not be obtained.

  On the other hand, when the well layer 13a is made of an AlInGaN layer, the carrier gas 103 containing nitrogen is preferably a mixed gas of nitrogen and hydrogen. When a carrier gas containing nitrogen and hydrogen was used to form a well layer made of an AlInGaN layer, the emission wavelength of the resulting well layer was made shorter than that for a well layer made of an InGaN layer. Rather, in the case of a well layer made of an AlInGaN layer, it was recognized that the light emission intensity was increased by growing with hydrogen. From the viewpoint of the increase in the emission intensity and the slight suppression effect of the non-light-emitting region, the well layer 13a is preferably composed of an AlInGaN layer, and the Al content in the AlInGaN layer is 1 to 20 mol relative to the total composition. % Is preferred. However, even if the well layer is an AlInGaN layer and is grown using the carrier gas 103 containing hydrogen and nitrogen, it is difficult to completely eliminate the non-light-emitting region.

  Note that TMI or TEI can be used as the group III element source containing In, TMG or TEG can be used as the group III element source containing Ga, and TMA or TEA can be used as the group III element source containing Al. Can be used.

  In the well layer forming step, the flow rate of ammonia gas 102 per unit time is preferably 1.5 L / min or more and 10 L / min or less.

  In the well layer forming step, the flow rate per unit time of the carrier gas 103 containing nitrogen is preferably 8 L / min or more and 30 L / min or less. When the carrier gas 103 further contains hydrogen, the proportion of hydrogen in the carrier gas 103 is preferably 0.5 mol% or more and 15 mol% or less. Here, the ratio of hydrogen in the carrier gas 103 means a mole percentage calculated by 100 times the value obtained by dividing the flow rate of hydrogen in the carrier gas 103 by the total flow rate of the carrier gas 103.

(Protective layer forming step)
FIG. 3 shows a protective layer forming step after the well layer forming step in the present embodiment. The protective layer forming step of the present embodiment is a step in which a GaN protective layer 13b is formed by supplying a Group III element material 111 containing Ga, an ammonia gas 112, and a carrier gas 113 containing nitrogen.

  Even if the first growth interruption step described later is performed without performing this protective layer forming step, the non-light-emitting region, which is the main factor that deteriorates the characteristics of the light-emitting element, is almost eliminated. However, according to the experimental results of the present inventors, when the protective layer forming step between the well layer forming step and the first growth interruption step is omitted, the well layer is formed after the first growth interruption step. It was found that a short-period uneven shape exists at the outermost surface, that is, the interface between the well layer and the barrier layer. This is because the hydrogen in the carrier gas supplied in the first growth interruption step has a strong effect of removing excess In remaining on the surface of the well layer 13a and extinguishing the non-light emitting region. This is presumably because an undesirable effect of etching the surface of the layer 13a is produced.

  This lack of flatness of the interface causes, for example, a decrease in internal quantum efficiency and an increase in internal loss within the cavity length in a semiconductor laser, and adversely affects the oscillation lifetime of the semiconductor laser. Therefore, it is desirable to improve the flatness of the interface in order to obtain better semiconductor laser lifetime characteristics.

  The purpose of the protective layer forming step in the present invention is to damage the outermost surface of the well layer formed in the well layer forming step by hydrogen in the carrier gas in the first growth interruption step described later (lack of flatness due to etching) ). By providing the protective layer 13b made of a nitride semiconductor between the well layer forming step and the first growth interruption step, the surface of the well layer 13a is directly hydrogen in the carrier gas in the first growth interruption step described later. Therefore, the flatness of the surface of the well layer 13a can be improved.

  The reason why excess In remaining on the surface of the well layer 13a can be removed in the first growth interruption step even though the surface of the well layer 13a is covered with the protective layer 13b is not clear, but probably It is presumed that excess In functions as a surfactant and excess In crawls up on the outermost surface of the protective layer. Therefore, in order to achieve both suppression of the non-light emitting region and improvement of the flatness of the well layer surface, the thickness of the protective layer 13b is preferably 0.25 nm or more and 1.2 nm or less. This thickness range corresponds to about 1 monolayer (monomolecular layer) or more and 4 monolayer (4 molecular layers) or less of a nitride semiconductor (GaN or AlGaN). When the thickness of the protective layer is less than 0.25 nm, it is not preferable because it is less than 1 monolayer of a nitride semiconductor and does not function sufficiently as a protective layer. On the other hand, if the thickness of the protective layer is greater than 1.2 nm, it is not preferable because it becomes difficult to eliminate the non-light-emitting region even if the first growth interruption step described later is performed.

  The temperature at which the protective layer 13b is formed in the protective layer forming step is preferably close to the temperature at which the well layer 13a is formed in the well layer forming step, and more preferably the same temperature. Thus, since the protective layer 13b can be formed immediately after the well layer 13a is formed, it is possible to prevent the outermost surface of the well layer from being damaged by heat and losing its flatness. .

  The protective layer 13b is composed of one or more nitride semiconductor layers, and at least the layer in direct contact with the well layer 13a is preferably a nitride semiconductor layer containing no In. As such a nitride semiconductor layer not containing In, a GaN layer, an AlGaN layer, or the like is preferably used. Therefore, the surface of the protective layer 13b that is in contact with the well layer is preferably composed of a single GaN layer, a single AlGaN layer, or a plurality of layers composed of a GaN layer and an AlGaN layer. Since the AlGaN layer is difficult to be etched by hydrogen, the protective layer 13b itself is etched by hydrogen in the carrier gas supplied in the first growth interruption step by using the protective layer 13b having such a configuration. Thus, it is possible to prevent the flatness of the surface from being impaired or the well layer 13a from being exposed due to the etching of the protective layer 13b. Moreover, a part of excess In remaining on the surface of the well layer 13a can be absorbed by the protective layer.

  Among the one or more layers constituting the protective layer 13b, when forming a nitride semiconductor layer that does not contain In, a group III element material 111 that contains Ga and does not contain In is used. Here, the group III element raw material containing Ga and not containing In is a raw material containing Ga as a group III element and not containing In, for example, a raw material containing only Ga and / or Al as a group III element. However, the present invention is not limited to this. Specifically, the AlGaN layer constituting the protective layer 13b is formed by supplying a raw material containing Ga and Al as the group III element raw material 111. Note that TMG or TEG can be used as a Group III element material containing Ga, and TMA or TEA can be used as a Group III element material containing Al.

  The flow rate of the ammonia gas 112 in the protective layer formation step is preferably equal to or greater than the flow rate of the ammonia gas in the well layer formation step, more preferably the flow rate of the ammonia gas 102 in the well layer formation step. 1.1 times or more and 3 times or less. This is because the ammonia gas 112 is not as much as hydrogen, but it can also have an effect of removing excess In, so that the non-light emitting region can be reduced by removing excess In while growing the protective layer 13b. Because.

  In the present embodiment, the carrier gas 113 used in the protective layer forming step can be a gas composed only of nitrogen or a mixed gas composed of nitrogen and hydrogen. When the carrier gas 113 is a gas composed only of nitrogen, the protective layer 13b itself is not etched, so that it has a sufficient function of protecting the well layer 13a, which is desirable in improving the flatness of the well layer 13a. . On the other hand, when the carrier gas 113 is a mixed gas composed of nitrogen and hydrogen, the protective layer 13b itself is easily etched, and although the improvement of the flatness of the well layer 13a is somewhat inferior, the excess remaining on the surface of the well layer 13a There is an advantage that In can be removed while growing the protective layer 13b. In the latter case, it is preferable to use an AlGaN layer rather than a GaN layer as the nitride semiconductor layer constituting the protective layer 13b.

  The proportion of hydrogen in the carrier gas 113 is preferably 1 mol% or more and 20 mol% or less. When the proportion of hydrogen is within this range, excess In remaining on the surface of the well layer 13a can be removed. If the ratio of hydrogen exceeds 20 mol%, the effect of etching the surface of the well layer 13a and the protective layer 13b becomes too strong, which is not preferable. Here, the ratio of hydrogen in the carrier gas 113 means a mole percentage calculated by 100 times the value obtained by dividing the hydrogen flow rate in the carrier gas 113 by (hydrogen flow rate in the carrier gas 113 + nitrogen flow rate). .

  The ratio of the flow rate of hydrogen in the carrier gas 113 to the flow rate of the ammonia gas 112 in the protective layer forming step is preferably 1 mol% or more and 35 mol% or less. Here, the ratio of the flow rate of hydrogen in the carrier gas 113 to the flow rate of the ammonia gas 112 means a molar percentage calculated by 100 times the value obtained by dividing the flow rate of hydrogen in the carrier gas by the flow rate of ammonia gas. . Although this ammonia gas 112 is not as much as hydrogen in the carrier gas 113, it can also produce an effect of removing excess In. This means that the flow rate of hydrogen having a strong etching effect can be suppressed by increasing the supply amount of the ammonia gas 112.

(First growth interruption process)
FIG. 4 shows a first growth interruption step after forming the protective layer 13b in the protective layer forming step. In the present embodiment, in the first growth interruption step, the supply of the group III element raw material 111 is stopped, and the carrier gas 123 composed of nitrogen and hydrogen is supplied together with the ammonia gas 122 for a predetermined time (hereinafter referred to as “first” Is a process of interrupting crystal growth. By this first growth interruption step, the non-light emitting region (excess In) peculiar to the well layer having a high In composition ratio can be removed to improve the light emission efficiency.

  As described above, in order to remove excess In remaining on the surface of the well layer 13a in a state where the surface of the well layer 13a is covered with the protective layer 13b, the protective layer is formed as a very thin layer. Therefore, ammonia gas 122 is additionally supplied during the first growth interruption step so that the protective layer 13b is not completely etched due to the excessive etching action of hydrogen in the carrier gas 123. Although this ammonia gas 122 is not as much as hydrogen in the carrier gas 123, it can also produce an effect of removing excess In. This means that the flow rate of hydrogen having a strong etching effect can be suppressed by increasing the supply amount of the ammonia gas 122. The ratio of the flow rate of hydrogen in the carrier gas 123 to the flow rate of the ammonia gas 122 is preferably set to be in the range of 1 mol% to 35 mol%. Here, the ratio of the flow rate of hydrogen in the carrier gas 123 to the flow rate of the ammonia gas 122 means a molar percentage calculated by 100 times the value obtained by dividing the hydrogen flow rate in the carrier gas by the ammonia gas flow rate.

  The flow rate of the ammonia gas 122 in the first growth interruption step is preferably equal to or greater than the flow rate of the ammonia gas 102 in the well layer formation step, more preferably 1.1 times or more and 3 times or less. . This is because the amount of ammonia gas 122 in the first growth interruption step is larger than the amount of ammonia gas 102 in the well layer formation step in which excess In could not be removed, thereby removing excess In. This is because the flow rate of hydrogen having a strong etching effect can be suppressed. As a result, the steepness of the layer change at the interface between the well layer and the protective layer or at the interface between the protective layer and the barrier layer can be improved. Steepness is the concept of how much heterogeneous semiconductor junctions are realized at the atomic level. If the heterointerface changes to a heterogeneous semiconductor layer on the monoatomic layer order, a sufficiently steep interface is formed. It can be said that the steepness is excellent.

  Further, the proportion of hydrogen in the carrier gas 123 used in the first growth interruption step is preferably 1 mol% or more and 20 mol% or less. When the proportion of hydrogen is in this range, excess In can be removed. If the ratio of hydrogen exceeds 20 mol%, the effect of etching the protective layer 13b becomes too strong, which is not preferable. Here, the ratio of hydrogen in the carrier gas 123 used in the first growth interruption step is 100 times the value obtained by dividing the hydrogen flow rate in the carrier gas 123 by (hydrogen flow rate in the carrier gas 123 + nitrogen flow rate). Means the mole percentage calculated in

  The predetermined time (first time) during which the first growth interruption step is performed is preferably 3 seconds or more and 180 seconds or less. If this time is shorter than 3 seconds, the effect of removing excess In is poor, and if it is longer than 180 seconds, the damage to the protective layer due to etching increases, and the flatness of the well layer surface deteriorates.

  Here, the temperature in the first growth interruption step is preferably close to the temperature at which the protective layer 13b is formed, and more preferably the same temperature. This is because it is very difficult to change and stabilize the substrate temperature within the optimal first time (3 seconds or more and 180 seconds or less). Since the change in the substrate temperature directly affects the effect of removing excess In, it is difficult to ensure reproducibility.

(Barrier layer formation process)
FIG. 5 shows the barrier layer forming step after the first growth interruption step. The barrier layer forming step is a step of forming a barrier layer 13c made of a nitride semiconductor by supplying a group III element raw material 131 containing Ga, an ammonia gas 132, and a carrier gas 133 made of nitrogen and hydrogen.

  As the barrier layer 13c, a single InGaN layer, a single GaN layer, a single AlGaN layer, a single InAlGaN layer, or a multilayer in which a plurality of these single layers are stacked can be used. . Of the nitride semiconductor layers constituting the barrier layer 13c, a layer directly in contact with the protective layer 13b (which may be a single layer as well as multiple layers) is a nitride semiconductor layer not containing In (for example, GaN More preferably, the layer is an AlGaN layer. This is because the effect of absorbing a small amount of In that cannot be completely removed in the first growth interruption step is great. Of the nitride semiconductor layers constituting the barrier layer 13c, the band gap energy of the layer directly in contact with the protective layer 13b is equal to or higher than the band gap energy of the protective layer 13b on the side in contact with the barrier layer 13c. More preferable examples of such a semiconductor layer include a GaN layer and an AlGaN layer. This improves the effect of confining carriers in the well layer and improves the lifetime characteristics of the semiconductor laser.

  On the other hand, a nitride semiconductor layer (not only a multi-layer but also a single layer) located on the surface of the barrier layer 13c opposite to the protective layer 13b is a GaN layer or a nitride semiconductor layer containing In (for example, GaN layer, InGaN layer, AlInGaN layer). This is because when the well layer is further laminated following the barrier layer 13c, it is easier to increase the wavelength by growing the well layer on the semiconductor layer as close as possible to the lattice constant of the well layer.

  As an example when the barrier layer 13c is composed of multiple layers, GaN layer / AlGaN layer / GaN layer, GaN layer / AlGaN layer / InGaN layer, GaN layer / AlGaN layer, AlGaN layer / GaN layer, AlGaN layer / InGaN layer, or Examples include InGaN layer / GaN layer / InGaN layer (note that each nitride semiconductor layer constituting the barrier layer 13c is described in order from the protective layer side). The barrier layer 13c composed of the InGaN layer / GaN layer / InGaN layer is a little left unremoved in the first growth interruption step by providing a GaN layer containing no In at a part of the barrier layer 13c. It has a function of absorbing indium.

  The group III element raw material 131 containing Ga used in the barrier layer forming step is a raw material containing Ga as a group III element, for example, a raw material containing only Ga as a group III element or Al and / or In other than Ga. Although the raw material to include is mentioned, it is not limited to these. Note that TMG or TEG can be used as a group III element source containing Ga, TMA or TEA can be used as a group III element source containing Al, and TMI or TEI as a group III element source containing In. Can be used. The various barrier layers 13c can be formed by using a group III element material containing only Ga or a group III element material containing Al and / or In in addition to Ga as the group III element material 131 containing Ga. . These group III element materials can be the same as the group III element materials used in the well layer forming step or the protective layer forming step.

  When the barrier layer 13c is composed of a GaN layer and / or an AlGaN layer that does not contain In at all, the thickness of the barrier layer 13c is preferably 6 nm or more and 18 nm or less. If the thickness of the layer is greater than 18 nm, the crystallinity of the barrier layer 13c itself deteriorates, and the non-light-emitting region grows in the well layer further formed thereon, which is not preferable. On the other hand, when the thickness of the layer is smaller than 6 nm, the effect of absorbing In described above is small, which is not preferable.

  When the barrier layer 13c is composed of an InGaN layer and / or an AlInGaN layer, the thickness is preferably 15 nm or more and 35 nm or less. If the barrier layer 13c is grown thick within this thickness range, even if it is the barrier layer 13c containing In, a slight amount of In that cannot be completely removed in the first growth interruption step is removed from the barrier layer 13c. It can be absorbed gradually during the growth process. This effect occurs because the In composition ratio in the barrier layer 13c is smaller than that in the well layer 13a and In is not saturated, and such a barrier layer 13c is formed thick within the above thickness range. This is thought to be because of this.

  The temperature at which the barrier layer 13c is formed in the barrier layer forming step is preferably close to the temperature at which the protective layer 13b is formed in the protective layer forming step, and more preferably the same temperature. This is because if the barrier layer 13c is formed at a temperature higher than the temperature (heat) at which the protective layer 13b is formed, the protective layer 13b may be etched to expose the well layer 13a therebelow.

  In the barrier layer forming step in the present embodiment, the carrier gas 133 always contains hydrogen. This is to maintain the effect of removing excess In by continuing to flow hydrogen even in the growth process of the barrier layer 13c.

  The inclusion of hydrogen in the carrier gas 133 is no exception even when the barrier layer 13c includes an InGaN layer. Generally, only nitrogen is used as the carrier gas when forming the InGaN layer. The reason for this is that if a small amount of unintentional hydrogen is mixed in a carrier gas composed of only nitrogen, the In composition ratio varies greatly and a desired InGaN layer cannot be formed. However, according to the experimental results of the present inventors, if the In composition ratio in the group III element is about 8 mol% or less, a desired InGaN layer can be formed even using a carrier gas containing hydrogen. all right. Moreover, the InGaN layer formed under the carrier gas condition containing hydrogen in this way is changed from the first growth interruption step to the barrier layer formation step as compared with that formed under the carrier gas condition containing no hydrogen. It was found that the variation in the In composition ratio was very small with respect to the change in the hydrogen concentration that occurred at the time of switching. This means that an InGaN layer can be used as the barrier layer 13c formed in the barrier layer forming step according to the present invention.

  The proportion of hydrogen in the carrier gas 133 is more preferably 1 mol% or more and 20 mol% or less. By supplying hydrogen in this range, it is possible to achieve both an effect of removing excess In and a barrier layer with good crystallinity. Here, the ratio of hydrogen in the carrier gas 133 is a molar percentage value calculated by 100 times the value obtained by dividing the hydrogen flow rate in the carrier gas 133 by (hydrogen flow rate in the carrier gas 133 + nitrogen flow rate). is there.

  Further, if the proportion of hydrogen in the carrier gas 133 is the same as the proportion of hydrogen in the carrier gas 123 in the first growth interruption step, the In composition ratio in the barrier layer 13c containing In (for example, InGaN, AlInGaN) Can be further suppressed, and the barrier level can be further stabilized.

  When the barrier layer 13c or the like is formed by crystal growth using the MOCVD method, if there is a large variation in gas flow rate between the respective steps (for example, between the first growth interruption step and the barrier layer formation step), the subsequent steps There is a risk that it is difficult to form a desired nitride semiconductor layer without stable crystal growth. In particular, ammonia gas has high viscosity resistance and low followability to changes in flow rate. Therefore, if the fluctuation of the ammonia gas flow rate between steps is large, stabilization of the reaction gas atmosphere tends to be delayed. For example, when the flow rate of the ammonia gas 122 in the first growth interruption step is larger than the flow rate of the ammonia gas 132 in the barrier layer formation step, it may be difficult to stably form the barrier layer 13c. From this viewpoint, the flow rate of the ammonia gas 132 is preferably the same as the flow rate of the ammonia gas 122 in the first growth interruption step. By doing so, the gas flow rate fluctuation at the time of switching from the first growth interruption step to the barrier layer formation step is reduced, and the desired barrier layer 13c can be formed.

  In the first embodiment, the crystal growth using the MOCVD apparatus has been described as an example, but the crystal growth may be performed using, for example, a MOMBE (metal organic molecular beam epitaxy) apparatus or an HVPE (hydride vapor phase epitaxy) apparatus. Needless to say, it is good.

<Embodiment 2>
With reference to the schematic cross-sectional view of FIG. 6, a method for manufacturing a nitride semiconductor light-emitting device according to Embodiment 2 of the present invention will be described. Compared with the first embodiment, the second embodiment continuously stops the supply of the group III element raw material between the first growth interruption step and the barrier layer forming step, and includes hydrogen and nitrogen together with the ammonia gas 142. It differs only in that the carrier gas 143 is supplied and a second growth interrupting step for interrupting crystal growth is additionally included for a predetermined time (hereinafter, sometimes abbreviated as “second time”). ing. Therefore, here, only the second growth interruption step will be mainly described in the present embodiment.

(Second growth interruption process)
In the second growth interruption step in the second embodiment, after the first growth interruption step shown in FIG. 4, the supply of the group III element raw material is continuously stopped as shown in FIG. Crystal growth is interrupted for a predetermined time while supplying a carrier gas 143 made of only nitrogen together with the gas 142. After this additional second growth interruption step, the present embodiment is performed by performing a barrier layer forming step (see FIG. 5) for forming the barrier layer 13c made of a nitride semiconductor as in the case of the first embodiment. The nitride semiconductor light emitting layer in Mode 2 can be formed.

  The purpose of the second growth interruption step is to recover the damage on the outermost surface of the protective layer 13b received in the first growth interruption step. In the first growth interruption step, excess In generated in the well layer 13a is removed through the protective layer 13b, and thus the surface of the protective layer 13b is easily damaged and its flatness is easily impaired. In particular, the lack of nitrogen element forming the protective layer 13b is remarkable, which causes crystal defects. Therefore, in the present embodiment, hydrogen contained in the carrier gas 123 supplied in the first growth interruption step is purged from the atmosphere in the vicinity of the substrate using the carrier gas 143 made of only nitrogen, and is a supply source of nitrogen. By supplying ammonia gas 142, recovery of damage on the outermost surface of the protective layer 13b is attempted.

  In order to enhance the recovery of the protective layer 13b, the predetermined time for performing the second growth interruption step (second time) is longer than the predetermined time for performing the first growth interruption step (first time). It is preferably long, and more preferably 1.2 times or more and 4 times or less of the first time. This is because the hydrogen contained in the carrier gas 123 used in the first growth interruption step can be more reliably purged from the atmosphere in the vicinity of the substrate by making the second time longer than the first time. This is because the recovery of damage to the protective layer is enhanced by taking a longer time than the first time required for removing In. Ammonia gas is not as strong as hydrogen, but has an etching effect, so it is not preferable to provide a growth interruption time longer than four times.

  In order to further enhance the recovery of the protective layer, it is preferable that the ratio of the flow rate of the ammonia gas 142 to the flow rate of the carrier gas 143 in the second growth interruption step is 30 mol% or more and 120 mol% or less. This increases the ability to protect or recover the surface of the damaged protective layer. Since ammonia gas is not as strong as hydrogen but has an etching effect, it is not preferable to perform the second growth interruption step at a flow rate exceeding 120 mol%. Here, the ratio of the flow rate of the ammonia gas 142 to the flow rate of the carrier gas 143 in the second growth interruption step is a mole percentage calculated by 100 times the value obtained by dividing the flow rate of the ammonia gas 142 by the flow rate of the carrier gas 143. Means the value of

  Furthermore, the total flow rate of the ammonia gas 142 and the carrier gas 143 in the second growth interruption step is preferably larger than the total flow rate of the ammonia gas 122 and the carrier gas 123 in the protective layer formation step. The effect of purging hydrogen contained in the carrier gas 123 used in the protective layer forming step from the atmosphere in the vicinity of the substrate is increased. More specifically, the total flow rate of the ammonia gas 142 and the carrier gas 143 in the growth interruption step is 1.2 to 3 times the total flow rate of the ammonia gas 122 and the carrier gas 123 in the protective layer formation step. Is preferred.

  Here, the temperature at the second time when the crystal growth is interrupted is preferably the same as the temperature at which the protective layer is formed in the protective layer forming step or the temperature at the first growth interrupting step. This is because if the temperature in the second time is higher than these temperatures, the protective layer may be etched and the well layer below it may be exposed.

<Embodiment 3>
With reference to the schematic cross-sectional view of FIG. 7, a method for manufacturing a nitride semiconductor light-emitting device according to Embodiment 3 of the present invention will be described. Compared with the first embodiment, the third embodiment continuously stops the supply of the group III element raw material between the first growth interruption step and the barrier layer forming step, and includes hydrogen and nitrogen together with the ammonia gas 152. The only difference is that the carrier gas 153 is supplied and a third growth interrupting step for interrupting crystal growth is additionally included for a predetermined time (hereinafter sometimes abbreviated as third time). Therefore, here, only the third growth interruption step will be mainly described in this embodiment.

(Third growth interruption process)
In the third growth interruption step in the third embodiment, after the first growth interruption step shown in FIG. 4, the supply of the group III element raw material is continuously stopped as shown in FIG. The crystal growth is interrupted for a predetermined time (third time) while supplying the carrier gas 153 containing hydrogen and nitrogen together with the gas 152. After this additional third growth interruption step, the barrier layer forming step (see FIG. 5) for forming the barrier layer 13c made of a nitride semiconductor is performed in the same manner as in the first embodiment. The nitride semiconductor light emitting layer in Mode 3 can be formed.

  The appropriate gas flow rate used in the first growth interruption step tends to be greatly different from the gas flow rate used in the barrier layer forming step. If the process proceeds from the first growth interruption step to the barrier layer formation step under such conditions, the change in gas flow rate increases, and it becomes difficult to form a desired barrier layer.

  The third growth interruption step in the third embodiment is a step for stabilizing the gas flow rate by reducing the change amount of the gas flow rate when shifting from the first growth interruption step to the barrier layer formation step. . This third growth interruption step facilitates the formation of the desired barrier layer 13c and improves the steepness of the layer change at the interface between the protective layer 13b (and well layer 13a) and the barrier layer 13c. .

  In order to further stabilize the gas flow rate, the flow rate of the ammonia gas 152 in the third growth interruption step is the same as the flow rate of the ammonia gas 132 in the barrier layer formation step, and the carrier gas 153 in the third growth interruption step. Is preferably the same as the flow rate of the carrier gas 133 in the barrier layer forming step. Thereby, the gas flow rate fluctuation at the time of transition from the first growth interruption step to the barrier layer forming step for forming the barrier layer can be further reduced.

  Further, when the proportion of hydrogen in the carrier gas 153 in the third growth interruption step is the same as the proportion of hydrogen in the carrier gas 133 used in the barrier layer forming step, the barrier layer 13c is changed due to the change in the hydrogen concentration. Since the composition variation (instability of the energy level of the barrier layer 13c) is small, it is possible to suppress a decrease in device yield due to fluctuation or deviation in the emission wavelength. This is particularly effective in the barrier layer 13c including an InGaN layer or an AlInGaN layer. Here, the ratio of hydrogen in the carrier gas 153 in the third growth interruption step is the molar percentage calculated by 100 times the value obtained by dividing the flow rate of hydrogen in the carrier gas 153 by the total flow rate of the carrier gas 153. Mean value.

  The predetermined time (third time) for performing the third growth interruption step is preferably 1 second or more and 5 seconds or less. If the third time is less than 1 second, the effect of stabilizing the gas flow rate, which is a function of the third growth interruption process, is not preferable because it is too small, and if the interruption time is increased beyond 5 seconds, the carrier gas 153 This is because hydrogen contained therein may etch the protective layer 13b.

  The temperature in the third growth interruption step is preferably the same as the temperature at which the protective layer 13b is formed in the protective layer formation step or the temperature in the first growth interruption step. This is because if the temperature in the third time is higher than these temperatures, the protective layer may be etched and the well layer below it may be exposed.

<Embodiment 4>
Embodiment 4 of the present invention additionally includes a third growth interruption step similar to that in Embodiment 3 between the second growth interruption step and the barrier layer formation step, as compared with Embodiment 2. The only difference is that

  In the third growth interruption step in the fourth embodiment, after the second growth interruption step shown in FIG. 6, the supply of the group III element raw material is continuously stopped as shown in FIG. While supplying the carrier gas 153 together with the gas 152, the crystal growth is interrupted for a predetermined time. After this additional third growth interruption step, the barrier layer forming step (see FIG. 5) for forming the barrier layer 13c made of a nitride semiconductor is performed in the same manner as in the first embodiment. The nitride semiconductor light emitting layer in Mode 4 can be formed.

  The effect of the third growth interruption step in the fourth embodiment is the same as that in the third embodiment. In addition, since the fourth embodiment includes the second growth interruption step, the same effect as that of the second embodiment can be obtained.

(Nitride semiconductor light emitting device)
Details of the laminated cross-sectional structure of the nitride semiconductor light-emitting device manufactured by the manufacturing method according to the above-described first to fourth embodiments will be described below.

  FIG. 9 is a schematic cross-sectional view showing a typical example of a nitride semiconductor light emitting device obtained by the manufacturing method of the present invention. FIG. 10 is a schematic cross-sectional view of a conventional nitride semiconductor light emitting device that does not have a protective layer as in the present invention. The laminated structure of the nitride semiconductor light emitting element in these figures corresponds to FIG. 1, and in particular, the light emitting layer 13 is shown in detail enlarged in the thickness direction. The light emitting layer 13 includes a plurality of well layers 13a and barrier layers 13c that are alternately and repeatedly stacked. In FIG. 9 showing the nitride semiconductor light emitting device of the present invention, a protective layer is provided between the well layers 13a and the barrier layers 13c. In FIG. 10, which shows a conventional nitride semiconductor light emitting device, no protective layer is formed.

  When the protective layer forming step is not applied, the barrier layer 13c and the well layer 13a thereon are provided as shown in FIG. 10, although depending on the amount of carrier gas hydrogen supplied in the first growth interruption step. Interface is flat (straight), whereas the interface between the well layer 13a and the barrier layer 13c on the well layer 13a tends to have a waveform with a relatively short period (the period w is short). That is, the well layer 13a includes a convex region 20 having a large thickness and a concave region 21 having a small thickness. This is mainly carried out between the well layer forming step for forming the well layer 13a and the barrier layer forming step for forming the barrier layer 13c. The cause is considered to be etching.

  The wave shape at the interface between the well layer 13a and the barrier layer 13c on the well layer 13a has a relatively regular shape and varies depending on the MOCVD conditions, but the wave shape period w is about 20 to 11 nm. The difference h was 50% or less of the average maximum thickness of the convex region 20.

  On the other hand, when the protective layer forming step according to the present invention is applied, the well layer 13a and the protective layer provided on the well layer 13a are provided depending on the amount of carrier gas hydrogen supplied in the first growth interruption step. The interface with the layer 13b or the protective layer 13b itself is substantially flat or has a wave shape having a relatively long period (long period w) compared to the period w in FIG. The interface between the barrier layer 13c and the well layer 13a thereon is flat (straight) as in FIG. The well layer 13a includes a convex region 20 having a large thickness and a concave region 21 having a small thickness, but the height difference h tends to be smaller than that of FIG. From this, by providing the protective layer 13b according to the present invention, an unintended well formed simultaneously with the removal of excess In distributed on the surface of the well layer 13a due to hydrogen in the carrier gas in the first growth interruption step. It is considered that the etching of the layer 13a was prevented.

  The wave shape at the interface between the well layer 13a and the protective layer 13b in FIG. 9 according to the present invention has a relatively regular shape and varies depending on the MOCVD conditions, but the wave shape period w is about 150 nm or more. The upper limit is infinite (flat). Further, the height difference h was 30% or less of the average maximum thickness of the convex region 20.

  Another feature of the well layer 13a formed by the manufacturing method of the present invention is that the fluctuation of the In composition ratio is very small. For example, when the In composition ratio in the convex region 20 and the concave region 21 of the well layer 13a shown in FIG. 9 is analyzed by EDX (energy dispersive X-ray fluorescence), the difference in In composition ratio between these regions is ± 1. It was less than mol%. That is, the convex region 20 and the concave region 21 of the well layer 13a differ only in thickness and tend to hardly change in the In composition ratio. This feature in which the In composition ratio does not change is preferable because the fluctuation of the wavelength in the nitride semiconductor light emitting device can be suppressed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

  The schematic cross-sectional view of FIG. 8 shows the laminated structure of the nitride semiconductor light emitting device fabricated in Example 1 of the present invention. In Example 1, a nitride semiconductor laser device was manufactured as the nitride semiconductor light emitting device of the present invention. The manufacturing method of the compound semiconductor laser device of Example 1 corresponds to the manufacturing method of the nitride semiconductor light emitting device according to Embodiment 1 described above.

  The nitride semiconductor laser device 10 of Example 1 includes an n-type GaN layer 201, an n-type AlGaN cladding layer 202, and an n-type GaN light guide that are sequentially stacked on the (0001) plane of a substrate (n-type GaN substrate) 11. The layer 203 includes an undoped InGaN light guide layer 204, a light emitting layer 13, an intermediate layer 205, a p-type AlGaN carrier block layer 206, a p-type AlGaN cladding layer 207, and a p-type GaN contact layer 208. Here, the stack from the n-type GaN layer 201 to the undoped InGaN light guide layer 204 corresponds to the n-type nitride semiconductor layer 12, and the stack from the intermediate layer 205 to the p-type GaN contact layer 208 is p-type nitride. It corresponds to the semiconductor layer 14.

In the manufacture of the nitride semiconductor laser element 10, the n-type GaN substrate 11 is first heated to 1050 ° C. and held at that temperature in the MOCVD apparatus, and includes TMG, ammonia gas, and Si, which are group III element materials. A doping gas (SiH ₄ ) was introduced to form an n-type GaN layer 201 having a thickness of 0.5 μm on the n-type GaN substrate 11. This n-type GaN layer 201 was formed in order to improve the surface morphology of the polished n-type GaN substrate 11 and reduce the surface residual stress strain to obtain a surface suitable for epitaxial growth.

Subsequently, TMA, which is a Group III element material, was also added to the MOCVD apparatus to form an n-type AlGaN cladding layer 202 having a thickness of 2.5 μm and a Si impurity concentration of 5 × 10 ¹⁷ atoms / cm ³ . In the n-type AlGaN cladding layer 202, the Al composition ratio in the group III element was 5 mol%.

Next, by stopping the introduction of TMA into the MOCVD apparatus and changing the amount of SiH ₄ introduced, an n-type GaN light guide having a thickness of 0.2 μm and a Si impurity concentration of 3 × 10 ¹⁷ / cm ³ is used. Layer 203 was formed.

  Thereafter, the substrate temperature was lowered to 800 ° C., TMG and TMI were supplied, and an undoped InGaN optical guide layer 204 having a thickness of 35 nm was formed.

On the InGaN light guide layer 204, the light emitting layer 13 having a multiple quantum well structure described later was formed. Further, an intermediate layer 205 having a thickness of 75 nm was formed on the light emitting layer 13. The intermediate layer 205 was composed of an undoped In _0.03 Ga _0.97 N layer having a thickness of 35 nm and an undoped GaN layer having a thickness of 40 nm, which were sequentially stacked.

Thereafter, the substrate temperature is raised again to 1050 ° C., the 20 nm thick AlGaN carrier blocking layer 206 to which Mg is added, the 0.6 μm thick p-type AlGaN cladding layer 207 to which Mg is added, and Mg are added. The p-type GaN contact layer 208 having a thickness of 0.1 μm was sequentially formed, and the crystal growth of the nitride semiconductor laser device 10 was completed. Here, the Al composition ratio in the group III element in the carrier block layer 206 was 20 mol%, and the Al composition ratio in the group III element in the p-type AlGaN cladding layer 207 was 5 mol%. Note that (EtCp) ₂ Mg was used as the source gas containing Mg.

Hereinafter, a method for forming the light emitting layer 13 which is an important feature of the present invention will be described in more detail. The light emitting layer 13 of this example includes an undoped In _0.13 Ga _0.87 N well layer (hereinafter simply referred to as an InGaN well layer) having a thickness of 3 nm, an undoped barrier layer having a thickness of 12 nm, and an undoped In _0.13 Ga layer having a thickness of 3 nm. _0.87 N well layers are sequentially stacked, and have an undoped GaN protective layer between the InGaN well layer and the undoped barrier. Here, the undoped barrier layer is formed by sequentially stacking three layers of a GaN layer having a thickness of 5 nm, an Al _0.03 GaN layer having a thickness of 2 nm, and a GaN layer having a thickness of 5 nm.

  In the first embodiment, in the well layer forming step of forming the InGaN well layer, TMI and TMG are used as a group III element source material containing In and Ga (see 101 in FIG. 2) at a temperature of 800 ° C. An ammonia gas (see 102 in FIG. 2) and a carrier gas (see 103 in FIG. 2) composed of 9 L / min of nitrogen were supplied to form an InGaN well layer having a thickness of 3 nm.

  Subsequently, in the protective layer forming step of forming a protective layer on the InGaN well layer, a group III element source material containing Ga and containing no In (111 in FIG. 3) at the same temperature of 800 ° C. as in the well layer forming step. TMG is used as a reference), and an ammonia gas of 3 L / min (see 112 in FIG. 3) and a carrier gas consisting of 9 L / min of nitrogen (see 113 in FIG. 3) are supplied, and the thickness is 0.52 nm. An undoped GaN protective layer was formed.

  Next, as the first growth interruption step, at the same temperature of 800 ° C. as in the protective layer formation step, the supply of the TMG group III element material is stopped, and ammonia gas of 6 L / min (see 122 in FIG. 4) At the same time, crystal growth was interrupted for 20 seconds (first time) while supplying a carrier gas composed of nitrogen of 8 L / min and hydrogen of 0.5 L / min (see 123 in FIG. 4).

  Furthermore, in the barrier layer forming step of Example 1, at the same temperature of 800 ° C., TMG or TMG and TMA group III element material (see 131 in FIG. 5), 6 L / min ammonia gas (in FIG. 5) 132) and a carrier gas composed of nitrogen of 8 L / min and hydrogen of 0.5 L / min (see 133 in FIG. 5) were supplied to form the barrier layer having the above three-layer structure.

  In the nitride semiconductor laser device obtained according to Example 1 as described above, there is no non-light-emitting region that easily occurs in a well layer having a high In composition ratio, and oscillation can be performed at a wavelength of 440 nm. It was. And with the improvement of the flatness of the interface of each layer of the light emitting layer, the laser oscillation lifetime has improved more than twice compared with the conventional one.

  The method for manufacturing a nitride semiconductor laser device according to Example 2 of the present invention corresponds to the method for manufacturing a nitride semiconductor light emitting device according to Embodiment 2 described above. That is, Example 2 is different from Example 1 only in that a second growth interruption process is added between the first growth interruption process and the barrier layer formation process.

  In Example 2, the well layer forming step for forming the AlInGaN well layer is performed at a temperature of 750 ° C. at the TMA, TMI, and TMG group III element materials (see 101 in FIG. 2), 3 L / min ammonia gas ( 2), and a carrier gas composed of 8.5 L / min nitrogen and 0.5 L / min hydrogen (see 103 in FIG. 2) to supply undoped AlInGaN having a thickness of 1.5 nm. A well layer was formed. In the AlInGaN well layer, the molar ratio of Al to the total composition of the well layer is about 0.02.

Subsequently, in the protective layer forming step of Example 2, at the same temperature of 750 ° C., group III element raw materials of TMA and TMG (see 111 in FIG. 3), 3 L / min of ammonia gas (in FIG. 3) 112), 6.5 L / min nitrogen and 2.5 L / min hydrogen carrier gas (see 113 in FIG. 3) is supplied to form an undoped Al _0.02 Ga _0.98 N protective layer having a thickness of 1 nm. did.

  In the first growth interruption step of the present Example 2, at the same temperature of 750 ° C., the supply of the group III element raw materials of TMA and TMG is stopped and together with ammonia gas (see 122 in FIG. 4) of 6 L / min. The crystal growth was interrupted for 15 seconds (first time) while supplying a carrier gas (see 123 in FIG. 4) composed of nitrogen of 8 L / min and hydrogen of 0.5 L / min.

  In the second growth interruption step of Example 2, at the same temperature of 750 ° C., ammonia gas (6 L / min in FIG. 6) was supplied while the supply of TMA and TMG was stopped following the first growth interruption step. 142) and a carrier gas consisting of 11 L / min of nitrogen (see 143 in FIG. 6) was supplied, and crystal growth was interrupted for 30 seconds (second time).

In the barrier layer forming step of Example 2, ammonia gas (FIG. 5) was used at the same temperature of 750 ° C. using a group III element material of TMA, TMG, and TMI (see 131 in FIG. 5). 132), and a carrier gas composed of 8 L / min nitrogen and 1.5 L / min hydrogen (see 133 in FIG. 5) is supplied to provide an 8 nm Al _0.02 Ga _0.98 N layer / 2 nm Al layer. _A barrier layer composed of _0.05 Ga _0.98 N layer / 2 nm In _0.04 Ga _0.96 N layer was formed. The number of well layers in the light emitting layer was three.

  In the nitride semiconductor laser device obtained according to Example 2 as described above, there was no non-light-emitting region likely to occur in a well layer having a high In composition ratio, and oscillation was possible at a wavelength of 465 nm. . In addition, since the non-light emitting region is eliminated in the well layer, the device yield and the light emission efficiency are greatly improved. Further, with the improvement of the flatness of the interface of each layer of the light emitting layer, the laser oscillation lifetime has been improved more than twice compared with the conventional one.

  The method for manufacturing a nitride semiconductor laser device according to Example 3 of the present invention corresponds to the method for manufacturing a nitride semiconductor light emitting device according to Embodiment 3 described above. That is, the third embodiment is different from the first embodiment only in that a third growth interruption step is added between the first growth interruption step and the barrier layer formation step.

  In the well layer forming step of forming the InGaN well layer in Example 3, at a temperature of 780 ° C., a group III element raw material of TMI and TMG (see 101 in FIG. 2), 3 L / min ammonia gas (in FIG. 2) 102) and a carrier gas composed of 9 L / min of nitrogen (see 103 in FIG. 2) were supplied to form an undoped InGaN well layer having a thickness of 2.5 nm.

Subsequently, in the first growth interruption step of the present Example 3, at the same temperature of 780 ° C., using TMA and TMG group III element materials (see 111 in FIG. 3), an ammonia gas of 3 L / min ( 112) in FIG. 3) and a carrier gas (see 113 in FIG. 3) consisting of 6.5 L / min of nitrogen and 2.5 L / min of hydrogen is supplied to form a 0.5 nm undoped GaN layer / 0. A protective layer consisting of a 5 nm Al _0.01 Ga _0.99 N layer was formed.

  In the first growth interruption step of Example 3, at the same temperature of 780 ° C., the supply of the group III element raw materials of TMA and TMG is stopped, together with 9 L / min of ammonia gas (see 122 in FIG. 4). The crystal growth was interrupted for 30 seconds (first time) while supplying a carrier gas (see 123 in FIG. 4) consisting of 8 L / min nitrogen and 1 L / min hydrogen.

  Next, in the third growth interruption process, at the same temperature of 780 ° C., ammonia gas (152 in FIG. 7) is supplied at the same temperature of 780 ° C. while the supply of TMA and TMG is stopped following the first growth interruption process. And a carrier gas (see 153 in FIG. 7) composed of 7.5 L / min of nitrogen and 0.5 L / min of hydrogen was supplied, and the crystal growth was interrupted for 3 seconds (third time).

In the barrier layer forming step of Example 3, at the same temperature of 780 ° C., the group III element raw materials of TMA, TMI and TMG (see 131 in FIG. 5) and 3 L / min of ammonia gas (in FIG. 5) 132), and a carrier gas composed of 5.5 L / min nitrogen and 2.5 L / min hydrogen (see 133 in FIG. 5) to supply an Al _0.05 In _0.02 Ga _0.93 N barrier layer having a thickness of 30 nm. Formed. The number of well layers in the light emitting layer is two.

  In the nitride semiconductor laser device obtained according to Example 3 as described above, there was no non-light-emitting region likely to occur in the well layer having a high In composition ratio, and oscillation was possible at a wavelength of 450 nm. . In addition, since the non-light emitting region is eliminated in the well layer, the device yield and the light emission efficiency are greatly improved. Further, the laser oscillation lifetime was improved with the improvement of the flatness of the interface of each layer of the light emitting layer.

  The method for manufacturing a nitride semiconductor laser device according to Example 4 of the present invention corresponds to the method for manufacturing a nitride semiconductor light emitting device according to Embodiment 4 described above. That is, Example 4 is different from Example 2 only in that a third growth interruption process is added between the second growth interruption process and the barrier layer formation process.

  In the well layer forming step of forming the InGaN well layer in Example 4, at a substrate temperature of 700 ° C., a group III element material of TMI and TMG (see 101 in FIG. 2), 3 L / min ammonia gas (FIG. 2) 102) and a nitrogen carrier gas of 9 L / min (see 103 in FIG. 2) were supplied to form an undoped InGaN well layer having a thickness of 1 nm.

  Subsequently, in the protective layer forming step of Example 4, at a temperature of 700 ° C., TMA and TMG group III element materials (see 111 in FIG. 3) were used, and an ammonia gas of 3 L / min (FIG. 3). 112) and a carrier gas composed of 9 L / min nitrogen (see 113 in FIG. 3) was supplied to form a 0.78 nm undoped GaN protective layer.

  In the first growth interruption step of the present Example 4, at the same temperature of 700 ° C., the supply of the TMG group III element material was stopped, and 8 L of ammonia gas (see 122 in FIG. 4) of 6 L / min. Crystal growth was interrupted for 40 seconds (first time) while supplying a carrier gas (see 123 in FIG. 4) composed of nitrogen / min and hydrogen of 0.5 L / min.

  Next, in the second growth interruption process, at the same temperature of 700 ° C., ammonia gas of 6 L / min (see reference numeral 142 in FIG. 5) is maintained while the supply of TMG is stopped following the first growth interruption process. And a carrier gas composed of nitrogen of 11 L / min (see 143 in FIG. 5) was supplied, and the crystal growth was interrupted for another 80 seconds (second time).

  Next, in the third growth interruption step, at the same temperature of 700 ° C., 3 L / min of ammonia gas (see 152 in FIG. 6) while stopping the supply of TMG following the second growth interruption step. At the same time, a carrier gas composed of 7.5 L / min nitrogen and 0.5 L / min hydrogen (see 153 in FIG. 6) was supplied, and the crystal growth was further interrupted for 3 seconds (third time).

  In the barrier layer forming step of Example 4, at the same temperature of 700 ° C., Group III element raw materials of TMI and TMG (see 131 in FIG. 5), 3 L / min ammonia gas (see 132 in FIG. 5) And a carrier gas composed of 7.5 L / min nitrogen and 0.5 L / min hydrogen (see 133 in FIG. 5) to form a 10 nm InGaN layer / 5 nm GaN layer / 10 nm InGaN layer A barrier layer was formed. The number of well layers in the light emitting layer is five.

  In the nitride semiconductor laser device obtained according to Example 4 as described above, there was no non-light-emitting region likely to occur in a well layer having a high In composition ratio, and oscillation was possible at a wavelength of 490 nm. . In addition, since the non-light emitting region is eliminated in the well layer, the device yield and the light emission efficiency are greatly improved. Further, the laser oscillation lifetime was improved with the improvement of the flatness of the interface of each layer of the light emitting layer.

  It should be understood that the embodiments and examples disclosed above are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The method for manufacturing a nitride semiconductor light emitting device according to the present invention is not limited to the formation of a nitride semiconductor laser device, but also various nitride semiconductor light emitting devices such as a nitride semiconductor light emitting diode device and a nitride semiconductor superluminescent diode device. It is possible to apply. These light emitting elements include various light emitting devices such as a high luminance white light source device combined with a phosphor, a high luminance blue or green light source device, an optical display device including an RGB (red green blue) light source, and a laser projector including an RGB light source. Can be applied to.

  DESCRIPTION OF SYMBOLS 10 Nitride semiconductor light-emitting device, 11 (n-type GaN) substrate, 12 n-type nitride semiconductor layer, 13 Light-emitting layer, 13a Well layer, 13b Protective layer, 13c Barrier layer, 14 p-type nitride semiconductor layer, 20 Convex region , 21 Concave region, 101, 111, 131 Group III element raw material, 102, 112, 122, 132, 142, 152 Ammonia gas, 103, 113, 123, 133, 143, 153 Carrier gas, 201 n-type GaN layer, 202 n-type AlGaN clad layer, 203 n-type GaN light guide layer, 204 undoped InGaN light guide layer, 205 intermediate layer, 206 p-type AlGaN carrier block layer, 207 p-type AlGaN clad layer, 208 p-type GaN contact layer.

Claims (22)

Manufacturing method of nitride semiconductor light emitting device including n-type nitride semiconductor layer, p-type nitride semiconductor layer, and light emitting layer formed between said n-type nitride semiconductor layer and said p-type nitride semiconductor layer Because
The light emitting layer includes one or more well layers made of a nitride semiconductor, one or more barrier layers made of a nitride semiconductor, and 1 made of a nitride semiconductor provided in contact with the well layer and the barrier layer. Including one or more protective layers and having an emission wavelength of 430 nm or more,
A well layer forming step of supplying a group III element source material containing In and Ga, ammonia gas, and a carrier gas containing nitrogen to form the well layer;
A protective layer forming step of forming a protective layer by supplying a Group III element source material containing Ga, ammonia gas, and a carrier gas containing nitrogen; and
A first growth interruption step of stopping the crystal growth for a predetermined time by stopping supply of the Group III element material containing Ga and supplying a carrier gas containing ammonia gas and nitrogen and hydrogen;
A nitride semiconductor light emitting device comprising: a group III element source material containing Ga, ammonia gas, and a barrier layer forming step for forming the barrier layer in this order by supplying a carrier gas containing nitrogen and hydrogen Device manufacturing method.   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, wherein the protective layer is provided in contact with the well layer on the p-type nitride semiconductor layer side.   3. The nitride according to claim 1, wherein the protective layer is composed of one or more nitride semiconductor layers, and at least a layer in direct contact with the well layer is a nitride semiconductor layer not containing In. For manufacturing a semiconductor light emitting device.   The method for manufacturing a nitride semiconductor light emitting element according to any one of claims 1 to 3, wherein the light emitting layer is exposed to a temperature of 900 ° C or higher and 1200 ° C or lower for 3 minutes or longer after the light emitting layer is formed.   The manufacturing method of the nitride semiconductor light-emitting device according to any one of claims 1 to 4, wherein a thickness of the p-type nitride semiconductor layer is 0.35 µm or more and 1 µm or less.   The method for manufacturing a nitride semiconductor light emitting element according to claim 1, wherein the protective layer has a thickness of 0.25 nm to 1.2 nm.   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, wherein the well layer has a thickness of 1 nm to 3.2 nm.   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, wherein the barrier layer has a thickness of 15 nm to 35 nm.   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, wherein the protective layer includes a GaN layer and / or an AlGaN layer.   The method for manufacturing a nitride semiconductor light emitting device according to claim 1, wherein the well layer is an InGaN layer or an AlInGaN layer.   The method for manufacturing a nitride semiconductor light emitting element according to claim 1, wherein the barrier layer includes at least one layer selected from the group consisting of an InGaN layer, a GaN layer, an AlGaN layer, and an InAlGaN layer.   The method for manufacturing a nitride semiconductor light emitting element according to claim 1, wherein a flow rate of ammonia gas in the protective layer forming step is equal to or greater than a flow rate of ammonia gas in the well layer forming step.   The carrier gas used in the protective layer forming step further contains hydrogen in addition to nitrogen, and the proportion of hydrogen in the carrier gas is 1 mol% or more and 20 mol% or less. A method for manufacturing a nitride semiconductor light emitting device.   The ratio of the flow rate of hydrogen in the carrier gas in the first growth interruption step to the flow rate of ammonia gas in the protective layer forming step is 1 mol% or more and 35 mol% or less. A method for producing a nitride semiconductor light emitting device according to claim 1.   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, wherein a ratio of hydrogen in the carrier gas used in the barrier layer forming step is 1 mol% or more and 20 mol% or less.   Between the first growth interruption step and the barrier layer forming step, the supply of the group III element raw material is stopped, and a carrier gas consisting of ammonia gas and nitrogen is supplied for a predetermined time. The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, further comprising a second growth interruption step of interrupting growth.   Between the first growth interruption step and the barrier layer forming step, the supply of the group III element raw material is stopped, and an ammonia gas and a carrier gas composed of hydrogen and nitrogen are supplied for a predetermined time, The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, further comprising a third growth interruption step of interrupting crystal growth.   Between the second growth interruption step and the barrier layer forming step, the supply of the group III element raw material is stopped, and a carrier gas composed of hydrogen and nitrogen is supplied together with the ammonia gas, and the crystal is grown for a predetermined time. The method for manufacturing a nitride semiconductor light emitting device according to claim 16, further comprising a third growth interruption step of interrupting the growth.   A light-emitting device comprising the nitride semiconductor light-emitting element manufactured using the method for manufacturing a nitride semiconductor light-emitting element according to claim 1. A nitride semiconductor light emitting layer formed on the surface of a substrate,
Including one or more well layers, one or more barrier layers, and one or more protective layers provided between and in contact with the well layers and the barrier layers,
The interface between the main surface of the well layer on the substrate side and the barrier layer is substantially flat, the other main surface of the well layer is covered with the protective layer, and the other surface of the well layer A nitride semiconductor light emitting layer, characterized in that the cross-sectional shape of the interface between the main surface and the protective layer is a wave shape.   21. The nitride semiconductor according to claim 20, wherein the protective layer is composed of one or more nitride semiconductor layers, and at least a layer in direct contact with the well layer is a nitride semiconductor layer not containing In. Luminescent layer.   A nitride semiconductor light emitting device comprising the nitride semiconductor light emitting layer according to claim 20.

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