JP2013155085A - Method for manufacturing gallium nitride compound semiconductor layer and method for manufacturing light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a GaN compound semiconductor layer, whereby the GaN compound semiconductor layer with a semipolar plane can be formed on a NdGaOsubstrate, and a method for manufacturing a light-emitting device.SOLUTION: A method for manufacturing a GaN compound semiconductor layer comprises epitaxially growing a GaN compound semiconductor 12 on a NdGaOsubstrate 11 wherein a principal plane on which the GaN compound semiconductor is grown is (012) plane, thereby forming the GaN compound semiconductor layer with a semipolar plane. The GaN compound semiconductor is grown so that the off angle formed by an axis in the [012] direction of a NdGaOcrystal in the NdGaOsubstrate 11 and a normal line of a surface of the NdGaOsubstrate 11 becomes ±5.0° or smaller.

Description

  The present invention relates to a method for manufacturing a gallium nitride (GaN) -based compound semiconductor layer and a method for manufacturing a light emitting device.

  As a substrate for epitaxial growth of a nitride compound semiconductor such as GaN, sapphire, silicon carbide (SiC), or the like is mainly used. Since these substrate materials have a large lattice mismatch with nitride compound semiconductors such as GaN compound semiconductors, various growth methods of nitride compound semiconductors to be grown on the substrate have been tried.

In order to eliminate the lattice mismatch between the substrate material and the nitride compound semiconductor, it is proposed to use a neodymium gallate (NdGaO ₃ : NGO) substrate whose pseudo lattice constant is close to that of a nitride compound semiconductor such as a GaN semiconductor. (For example, see Patent Documents 1 and 2).

  Recently, in order to suppress a decrease in the light emission efficiency of the light emitting device due to the polarity of the (0001) plane (c plane) of the GaN-based compound semiconductor, GaN having a nonpolarity or a semipolar plane with a small polarity There has been a demand for a GaN substrate on which a semiconductor is grown. In particular, when manufacturing a pure green laser or the like among the three primary colors of light, red, green, and blue, a conventional c-plane GaN-based compound semiconductor has a large In composition in the GaN-based semiconductor. Distortion increases and the negative effect of having polarity increases. Therefore, it is difficult to manufacture a pure green laser or the like using a polar c-plane GaN-based compound semiconductor as a nitride-based compound semiconductor.

  Therefore, if a GaN substrate formed by growing a nitride-based compound semiconductor such as a GaN-based compound semiconductor having a small polarity such as a semipolar surface or a nonpolar surface can be manufactured, the adverse effects of having a polarity can be eliminated. Therefore, it is considered that a light emitting device such as a pure green laser having a high light emission efficiency can be manufactured.

  Here, FIG. 21 shows a diagram in which the atomic arrangement of the (011) plane of the NGO crystal is associated with the atomic arrangement of the (0001) plane (c-plane) of the GaN crystal. As shown in FIG. 21, in the (011) plane of the NGO crystal, the length of the a-axis of the NGO crystal and the lattice constant in the [11-20] direction of the GaN crystal are almost the same. Therefore, a GaN substrate made of a GaN crystal is said to be a substrate that can solve the problem of lattice irregularities when sapphire, SiC, or the like is used as a base substrate. Accordingly, a technique for growing c-plane GaN on a (011) -plane NGO substrate using a hydride vapor phase epitaxy (HVPE) method has been developed. When GaN is grown on the (011) -plane NGO substrate, the c-plane GaN crystal becomes a pseudo lattice match on the (011) -plane NGO substrate, and the GaN crystal grows in the c-axis direction. c-plane.

JP-A-8-186078 JP-A-8-186329

  However, when a non-polar or semipolar GaN substrate that can be applied to a green laser diode (LD) or the like by this method is to be manufactured, the GaN-based semiconductor is made thicker and GaN is increased. It is necessary to cut the substrate vertically and process it so that the nonpolar surface of the GaN crystal becomes the main surface, or to cut the GaN substrate obliquely and process it so that the semipolar surface of the GaN crystal becomes the main surface.

  Therefore, after growing a GaN-based compound semiconductor on an NGO substrate, the method of processing the GaN substrate so that the nonpolar or semipolar surface of the GaN crystal becomes the main surface is a size that can be used for an actual device. It is difficult to produce a GaN substrate (for example, 2 inches). Even if a GaN substrate having a size (for example, 2 inches) used for a device can be manufactured, only a rectangular GaN substrate having a predetermined size (for example, several tens of mm) can be manufactured.

  Therefore, when manufacturing light-emitting devices such as pure green lasers with good light emission efficiency, nitride-based compound semiconductors such as nonpolar or non-polar GaN-based compound semiconductors with no polarity on the NGO substrate are used. The advent of a method for producing a GaN-based compound semiconductor layer that can be grown is demanded.

  The present invention has been made in view of the above, and provides a method for manufacturing a GaN-based compound semiconductor layer and a method for manufacturing a light-emitting device capable of forming a semipolar plane GaN-based compound semiconductor layer on an NGO substrate. The purpose is to do.

  In order to solve the above-described problems and achieve the object, the present inventors have intensively studied a method for manufacturing a gallium nitride-based compound semiconductor layer and a method for manufacturing a light-emitting device. As a result, attention was paid to the fact that the atomic spacing of Ga or Nd in the NGO crystal and the atomic spacing in the (1-100) direction of the GaN crystal substantially coincide. As for the GaN grown on the (012) plane NGO crystal, it was clarified that the semipolar plane GaN crystal grows preferentially. Based on the obtained knowledge, it was found that a semipolar plane GaN-based semiconductor can be formed on a (012) plane NGO substrate. The present invention has been completed based on such knowledge.

In the method for producing a gallium nitride compound semiconductor layer of the present invention, a gallium nitride compound semiconductor is epitaxially grown on a NdGaO ₃ substrate whose principal surface on which a gallium nitride compound semiconductor is grown is a (012) plane, and a semipolar plane nitridation is performed. A gallium compound semiconductor layer is formed.

In a preferred embodiment of the present invention, it is preferable that the off angle formed between the normal line of the NdGaO ₃ substrate of NdGaO ₃ crystal [012] axis and the NdGaO ₃ substrate surface is grown below ± 5.0 ° .

As a preferred embodiment of the present invention, the NdGaO ₃ substrate is heated at a temperature of 600 ° C. or higher and 900 ° C. or lower while supplying an inert gas into the growth furnace before epitaxially growing the gallium nitride compound semiconductor layer. , after cleaning the NdGaO ₃ substrate surface, it is preferable to grow the semi-polar plane gallium nitride-based compound semiconductor on the NdGaO ₃ substrate.

As a preferred embodiment of the present invention, it is preferable that the substrate temperature of the NdGaO ₃ substrate is 550 ° C. or higher and 650 ° C. or lower to grow a semipolar plane gallium nitride compound semiconductor.

In a preferred embodiment of the present invention, the NdGaO ₃ on the substrate, after forming the gallium nitride-based compound semiconductor layer, it is preferable to obtain the NdGaO ₃ substrate peeling to gallium nitride-based compound semiconductor layer.

The method for manufacturing a light-emitting device according to the present invention includes epitaxial growth of a gallium nitride compound semiconductor on a NdGaO ₃ substrate whose main surface on which a gallium nitride compound semiconductor is grown is a (012) plane, and a gallium nitride compound having a semipolar plane. A stacked body in which one or more semiconductor layers are stacked is formed, and the gallium nitride compound semiconductor layer is p-type or n-type.

The method for manufacturing a light-emitting device according to the present invention includes epitaxial growth of a gallium nitride compound semiconductor on a NdGaO ₃ substrate whose main surface on which a gallium nitride compound semiconductor is grown is a (012) plane, and a gallium nitride compound having a semipolar plane. After forming a stacked body in which one or more semiconductor layers are stacked, the stacked body obtained by peeling off the NdGaO ₃ substrate is used as the first stacked body, and gallium nitride is formed on the first stacked body. Epitaxially growing a compound semiconductor to form a second stacked body in which one or more gallium nitride compound semiconductor layers having a semipolar plane are stacked, and the second stacked body is either p-type or n-type, or Both gallium nitride compound semiconductor layers are provided. In the present invention, the first laminate obtained by peeling from the NdGaO ₃ substrate is also referred to as a gallium nitride free-standing substrate (GaN free-standing substrate).

  According to the present invention, since the pseudo lattice constants of the Ga atomic spacing of the NGO crystal and the [11-20] direction atomic spacing of the GaN crystal substantially coincide with each other, the GaN crystal is c c around the coincident axis. Since the GaN crystal can be preferentially grown on the semipolar plane on the (012) plane NGO substrate by tilting the axis, the semipolar plane GaN-based compound semiconductor layer is formed on the NGO substrate. Can be formed.

FIG. 1 is a diagram illustrating an example of a method for manufacturing a GaN-based compound semiconductor layer according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the crystal structure of the (012) plane of the NGO crystal of the NGO substrate. FIG. 3 is a diagram illustrating an example of the relationship between the c-axis angle, the light emission efficiency, and the spontaneous polarization. FIG. 4 is a diagram simply showing the configuration of the light emitting device. FIG. 5 is an explanatory diagram of the periodic layer. FIG. 6 is a diagram simply illustrating another configuration of the light emitting device. FIG. 7 is a flowchart illustrating an example of a method for manufacturing a light emitting device according to an embodiment of the present invention. FIG. 8 is a diagram showing a part of the manufacturing process of the light emitting device. FIG. 9 is a diagram illustrating a part of the manufacturing process of the light emitting device. FIG. 10 is a diagram illustrating a part of the manufacturing process of the light emitting device. FIG. 11 is a diagram illustrating a part of the manufacturing process of the light emitting device. FIG. 12 is a flowchart showing an example of a manufacturing method of another configuration of the light emitting device according to the embodiment of the present invention. FIG. 13 is a diagram illustrating a part of the manufacturing process of the light emitting device. FIG. 14 is a diagram illustrating a part of the manufacturing process of the light emitting device. FIG. 15 is a diagram showing the results of X-ray diffraction obtained by measuring the GaN thin film in Example 1. FIG. 16 is a diagram showing a result of X-ray diffraction obtained by measuring the GaN thin film in Comparative Example 1. FIG. 17 is a diagram showing an X-ray diffraction pattern measured by setting Psi to 20 °. FIG. 18 is an explanatory diagram showing the relationship between the NGO substrate having the (012) plane of the NGO crystal and the c-plane of the GaN crystal. FIG. 19 is a graph showing the relationship between the off-angle of the NGO substrate having the (012) plane of the NGO crystal and the inclination of the c-axis of the GaN thin film. FIG. 20 is a diagram showing the relationship between the cleaning temperature of the NGO substrate and the inclination of the c-axis of the GaN thin film. FIG. 21 is a diagram in which the atomic arrangement of the (011) plane of the NGO crystal is associated with the atomic arrangement of the (0001) plane (c-plane) of the GaN crystal.

  DESCRIPTION OF EMBODIMENTS Hereinafter, modes for suitably carrying out the present invention (hereinafter referred to as embodiments) will be described in detail. In addition, this invention is not limited by the content described in the following embodiment and an Example. In addition, constituent elements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be appropriately combined or may be appropriately selected and used.

<GaN compound semiconductor layer>
A GaN-based compound semiconductor layer obtained using the method for manufacturing a GaN-based compound semiconductor layer according to this embodiment will be described. The GaN-based compound semiconductor layer is obtained by epitaxially growing a GaN-based compound semiconductor on an NGO substrate (hereinafter referred to as “NGO substrate”) whose main surface on which the GaN-based compound semiconductor is grown is a (012) plane. A GaN-based compound semiconductor has a semipolar surface. As will be described later, the GaN-based compound semiconductor layer is manufactured by using the method for manufacturing a GaN-based compound semiconductor layer according to this embodiment. The GaN-based compound semiconductor layer may be composed of one layer or a plurality of layers. In the present specification, the main surface refers to a surface on which a GaN-based compound semiconductor is grown.

  In the present embodiment, the semipolar plane is a plane having a predetermined angle with the c-plane of the GaN crystal, and examples of the semipolar plane include (11-24) plane. The c-plane is a plane perpendicular to the hexagonal c-axis, and the c-plane is a (0001) plane. Further, the nonpolar plane is a plane perpendicular to the c plane such as the a plane or the m plane. As the nonpolar plane, the a plane is the (11-20) plane, and the m plane is (10− 10) surface.

<Method for producing GaN-based compound semiconductor layer>
FIG. 1 is a diagram showing an example of a method for manufacturing a GaN-based compound semiconductor layer according to this embodiment. As shown in FIG. 1, the manufacturing method of the GaN-based compound semiconductor layer according to this embodiment includes the following steps.
A) NGO substrate preparation process for preparing the NGO substrate 11 (step S11)
B) GaN-based compound semiconductor layer forming step of epitaxially growing a GaN-based compound semiconductor on the NGO substrate 11 to form a semipolar plane GaN-based compound semiconductor layer 12 (step S12)
C) Substrate peeling step for peeling the GaN-based compound semiconductor layer 12 from the NGO substrate 11 (step S13)

  An NGO substrate 11 whose main surface is the (012) surface is prepared. The NGO substrate 11 is a substrate on which a GaN-based compound semiconductor having a semipolar plane is epitaxially grown on the main surface. The main surface is cut out from the NGO ingot grown by the pulling method as (012), polished, and the NGO substrate 12 is ultrasonically cleaned in an acetone solution and then degreased, and then ultrasonically cleaned in methanol and ultrapure water. Then, the foreign matter adhering to the surface of the NGO substrate 11 is removed (NGO substrate preparation step: step S11).

As a substrate capable of epitaxially growing a GaN-based compound semiconductor, generally, for example, a silicon (Si) substrate, a sapphire (Al ₂ O ₃ ) substrate, a gallium arsenide (GaAs) substrate, a gallium nitride (GaN) substrate, Examples include a group III nitride base substrate such as an aluminum nitride (AlN) substrate, a substrate having a perovskite crystal structure such as an NGO substrate, and the like. In the present embodiment, the substrate that can be epitaxially grown is preferably a substrate having a perovskite crystal structure, but among them, the NGO substrate 11 is preferably used from the viewpoint of high lattice matching with the GaN-based compound semiconductor layer 12. .

  From the viewpoint of growing a single crystal of a GaN-based compound semiconductor, the cleanness of the surface of the NGO substrate 11 is important for the NGO substrate 11. In particular, the main surface of the NGO substrate 11 (refers to the surface of the substrate that does not contact the inner wall of the growth reactor; the same applies hereinafter) and the rear surface (refers to the surface of the substrate that contacts the inner wall of the growth reactor; the same applies hereinafter). Since it cannot be etched, it is necessary to increase the cleanliness before putting it into the growth furnace. For this reason, it is preferable that the main surface of the NGO substrate 11 is etched and then introduced into the growth furnace. Etching methods include etching with an alkaline solvent and etching with a halogen-based gas.

  After the NGO substrate 11 is put into the growth furnace, before the GaN compound semiconductor is epitaxially grown on the NGO substrate 11, the inert gas is supplied at a temperature of 600 ° C. or more and 900 ° C. or less and the supply amount of the inert gas is increased. It is preferable to perform cleaning to volatilize and remove deposits and the like on the surface of the NGO substrate 11 by performing heat treatment at 1500 to 2000 sccm for 5 to 10 minutes while supplying the growth furnace. By performing this cleaning, the inclination of the c-axis of the GaN-based compound semiconductor layer 12 grown on the NGO substrate 11 is such that the (012) plane of the NGO crystal of the NGO substrate 11 and the c-axis of the GaN-based compound semiconductor layer 12 are As a result, a semipolar GaN-based compound semiconductor layer can be formed.

Examples of the inert gas include nitrogen (N ₂ ) gas, argon (Ar) gas, helium (He) gas, and the like.

  A GaN-based compound semiconductor is epitaxially grown on the NGO substrate 11 to form a semipolar plane GaN-based compound semiconductor layer 12 (GaN-based compound semiconductor layer forming step: step S12).

  In the present embodiment, the semipolar surface is a surface having a predetermined angle with the c-plane as described above, and examples of the semipolar surface include the (11-24) surface.

  The method for growing the GaN-based compound semiconductor is not particularly limited as long as it is a method capable of epitaxial growth, and conventionally known methods can be mentioned. From the viewpoint of growing a highly crystalline GaN-based compound semiconductor, GaN Examples of the method for forming the compound semiconductor layer 12 include metal organic chemical vapor deposition (MOVPE), metal organic chemical vapor deposition (MOCVD), and molecular beam growth. Examples thereof include vapor phase methods such as (MBE: Molecular Beam Epitaxy) method and HVPE method. The GaN-based compound semiconductor layer 12 can be grown using any one of these MOVPE methods, MBE methods, and HVPE methods. Among them, the HVPE method is particularly preferable from the viewpoint of high crystal growth rate in the production of a GaN free-standing substrate.

  The off angle, which is the angle formed by the axis in the crystal [012] direction of the NGO substrate 11 and the normal line of the surface of the NGO substrate 11, is preferably ± 5.0 ° or less. This is because the GaN-based compound semiconductor having a semipolar orientation is formed because the bond direction on the outermost surface of the NGO crystal is too large from the normal to the surface of the NGO substrate 11 when the off-angle increases. It is because it becomes impossible to grow.

  When the GaN-based compound semiconductor is epitaxially grown on the NGO substrate 11, the GaN-based compound semiconductor layer 12 is preferably formed with the substrate temperature of the NGO substrate 11 being 550 ° C. or higher and 650 ° C. or lower, more preferably 550 ° C. or higher and 600 ° C. or lower. It is. In the case of semipolar growth, it is necessary to reflect the direction of the bonding hand on the outermost surface of the NGO substrate 11, and in the growth at a high temperature of 650 ° C. or higher, the migration at the surface at the time of growth becomes large, so it is most easily oriented. It is considered that a semipolar plane cannot be obtained because of growth on the plane.

  Thereafter, the GaN-based compound semiconductor layer 12 is peeled from the NGO substrate 11 (substrate peeling step: step S13). Thereby, the GaN-based compound semiconductor layer 12 is obtained. The GaN-based compound semiconductor layer 12 obtained by peeling from the NGO substrate 11 is also referred to as a gallium nitride free-standing substrate (GaN free-standing substrate).

  In the method of manufacturing a GaN-based compound semiconductor layer according to this embodiment, a GaN-based compound semiconductor layer 12 having a semipolar surface is obtained by epitaxially growing a GaN-based compound semiconductor on an NGO substrate 12 whose main surface is a (012) plane. It is done.

  FIG. 2 is an explanatory diagram showing the crystal structure of the (012) plane of the NGO crystal of the NGO substrate 11. As shown in FIG. 2, the Ga interval (for example, 0.5426 nm) of the NGO crystal and the atomic interval (for example, 0.5524 nm) in the [11-20] direction of the GaN crystal substantially coincide. For this reason, a GaN crystal having a semipolar plane (for example, (11-24) plane) can be preferentially grown on the NGO substrate 11 whose main surface is the (012) plane, and the GaN crystal is semipolar. It can be said that it will grow to the surface. Thereby, the semipolar plane GaN-based compound semiconductor layer 12 can be formed on the NGO substrate 11 whose main surface is the (012) plane.

  Therefore, according to the GaN-based compound semiconductor layer manufacturing method of the present embodiment, the semipolar GaN-based compound semiconductor layer 12 can be obtained from the NGO substrate 11 whose main surface is the (012) plane.

  FIG. 3 is a diagram illustrating an example of the relationship between the c-axis angle, the light emission efficiency, and the spontaneous polarization. FIG. 3 shows an example of spontaneous polarization and light emission efficiency when a GaN layer, an InGaN layer, and a GaN layer are stacked, and the InGaN layer is 3 nm and contains about 10% In. As shown in FIG. 3, the spontaneous polarization is better as it is closer to 0, and the light emission efficiency becomes higher. For example, the (11-24) plane, which is one of the semipolar planes, is at an angle of about 40 ° from the c-axis, and is a nonpolar plane (eg, (11-20) plane, (1-100) plane). It has a luminous efficiency of about 70%. Moreover, the semipolar plane (for example, (11-24) plane) has higher luminous efficiency than the (0001) plane which is a polar plane. Therefore, by forming the semipolar plane GaN-based compound semiconductor layer 12 on the NGO substrate 12, a light-emitting element having high light emission efficiency can be obtained using the GaN-based compound semiconductor layer 12. As a result, as will be described later, when a light-emitting device including a GaN-based compound semiconductor layer 12 having a semipolar surface is applied to a green LED or LD, a green LED or LD using an InGaN layer that has conventionally had low light emission efficiency. Luminous efficiency can be significantly improved.

<Light emitting device>
Next, a case where a GaN-based compound semiconductor layer obtained using the method for manufacturing a GaN-based compound semiconductor layer according to the present embodiment is applied as a light emitting device will be described. This embodiment demonstrates the case where it applies to LED as a light emitting device. FIG. 4 is a diagram simply showing the configuration of the light emitting device. As shown in FIG. 4, the light emitting device 20 includes a stacked body 21, a first electrode 22, and a second electrode 23. The stacked body 21 is formed by stacking a plurality of semipolar GaN-based compound semiconductor layers. In the present embodiment, the stacked body 21 includes a first stacked body 24 and a second stacked body 25 formed on the first stacked body 24.

  The first stacked body 24 has a buffer layer 31 made of a GaN layer and a GaN-based compound semiconductor layer of an n-type GaN layer 32, and is configured by stacking in this order.

  The second stacked body 25 includes a GaN-based compound semiconductor layer including a periodic layer 33 in which 10 layers of n-type GaN layers / InGaN layers are stacked, a p-type AlGaN layer 34, and a p-type GaN layer 35. They are stacked in order.

  As shown in FIG. 5, the periodic layer 33 includes an n-type GaN layer 33-1 and an InGaN layer 33-2 as one set, and a set of n-type GaN layer / InGaN layer is stacked in x layers. Configured. x should just be an integer greater than or equal to 1, and the periodic layer 33 can be suitably made into arbitrary lamination | stacking number. Further, the periodic layer 33 has a function as a layer that absorbs stress between the NGO substrate 12 and the stacked body 21.

  The stacked body 21 has a plurality of p-type or n-type gallium nitride compound semiconductor layers. The first stacked body 24 includes an n-type GaN-based compound semiconductor layer, and the second stacked body 25 includes one or both of a p-type and an n-type gallium nitride-based compound semiconductor layer.

  The buffer layer 31, the n-type GaN layer 32, the p-type AlGaN layer 34, and the p-type GaN layer 35 are single layers, but each may be formed of a plurality of layers.

  The first electrode 22 is formed on the outermost layer of the p-type GaN layer 35. The second electrode 23 is formed on the exposed main surface of the n-type GaN layer 32. The first electrode 22 and the second electrode 23 are formed of, for example, a mixture containing one or more of aluminum (Al), silver (Ag), and indium (In).

  As described above, the light-emitting device 20 includes a GaN-based compound semiconductor layer obtained using the method for manufacturing a GaN-based compound semiconductor layer according to this embodiment. It includes a laminate 21 in which one or more GaN-based compound semiconductor layers are laminated. As will be described later, the first stacked body 24 is formed on the (012) -plane NGO substrate 11, and the second stacked body 25 is formed on the first stacked body 24. Therefore, each GaN-based compound semiconductor layer included in the first stacked body 24 and the second stacked body 25 is a semipolar surface. In other words, the first stacked body 24 (buffer layer 31, n-type GaN layer 32) and the second stacked body 25 (periodic layer 33, p-type AlGaN layer 34, and p-type GaN layer 35) are all. This is a semipolar plane GaN-based compound semiconductor layer.

  Therefore, the light emitting device 20 includes the first stacked body 24 and the second stacked body configured by stacking a plurality of semipolar GaN-based compound semiconductor layers formed on the NGO substrate 12 having the (012) plane. Since it is a light-emitting device formed including 25, it can be used as a light-emitting element having high light emission efficiency using a GaN-based compound semiconductor.

  Further, the light emitting device 20 is obtained by peeling the NGO substrate 11 from the first stacked body 24 configured by stacking a plurality of GaN-based compound semiconductor layers, but the present embodiment is not limited to this. A laminated structure formed by laminating a plurality of GaN-based compound semiconductor layers on the NGO substrate 11 may be used as a light emitting device as it is.

  FIG. 6 is a diagram simply illustrating another configuration of the light emitting device. As shown in FIG. 6, the light emitting device 30 includes an NGO substrate 11 whose main surface 11 a on which a GaN-based compound semiconductor is grown is a (012) plane, and a GaN-based compound semiconductor layer according to this embodiment on the NGO substrate 11. A stacked body 21 that is formed by stacking a plurality of layers, a first electrode 22, and a second electrode 23 is provided. As described above, the stacked body 21 is configured by stacking a plurality of semipolar GaN-based compound semiconductor layers.

  The stacked body 21 includes, in order from the NGO substrate 11 side, a buffer layer 31, an n-type GaN layer 32, a periodic layer 33 in which 10 n-type GaN layers / InGaN layers are stacked, and a p-type compound semiconductor layer. An AlGaN layer 34 and a p-type GaN layer 35 are stacked in this order.

  As described above, the light emitting device 30 includes the stacked body 21 configured by stacking a plurality of GaN-based compound semiconductor layers obtained by using the method for manufacturing a GaN-based compound semiconductor layer according to this embodiment. Since the GaN-based compound semiconductor layer according to this embodiment is formed on the (012) -plane NGO substrate 12 as described above, any of the GaN-based compound semiconductor layers according to this embodiment has a semipolar surface. It has become. That is, the buffer layer 31, the n-type GaN layer 32, the periodic layer 33, the p-type AlGaN layer 34, and the p-type GaN layer 35 constituting the stacked body 24 are all GaN-based compound semiconductor layers having a semipolar plane. is there. Therefore, the light emitting device 30 according to the present embodiment is a light emitting device formed by including the stacked body 21 configured by stacking a plurality of semipolar GaN-based compound semiconductor layers on the NGO substrate 12 having the (012) plane. Since it is a device, it can be used as a light-emitting element having high luminous efficiency using a GaN-based compound semiconductor.

<Method for manufacturing light-emitting device>
Next, a method for manufacturing the light emitting device 20 according to this embodiment will be described. FIG. 7 is a flowchart showing an example of a method for manufacturing the light emitting device 20 according to the present embodiment. As shown in FIG. 7, the method of manufacturing the light emitting device 20 according to the present embodiment includes the following steps.
A) NGO substrate preparation process for preparing the NGO substrate 11 (step S21)
B) A GaN-based compound semiconductor is epitaxially grown on an NGO substrate 11 whose main surface on which a GaN-based compound semiconductor is grown is the (012) plane, and a semipolar GaN-based compound semiconductor layer (buffer layer 31, n-type GaN) is grown. Step of forming a first stacked body 24 (step S22) for forming a stacked structure having the layer 32) as a first stacked body (GaN free-standing substrate) 24
C) Substrate peeling step for peeling the first laminate 24 from the NGO substrate 11 (step S23)
D) A stacked structure in which a GaN-based compound semiconductor is epitaxially grown on the first stacked body 24 and has a semipolar plane GaN-based compound semiconductor layer (periodic layer 33, p-type AlGaN layer 34, and p-type GaN layer 35). 2nd laminated body formation process (step S24) which forms a body as the 2nd laminated body 25
E) Etching process of protecting a part of the surface of the p-type GaN layer 35 with a resist and then etching until a part of the n-type GaN layer 32 is exposed (step S25).
F) Electrode forming step of forming the first electrode 22 and the second electrode 23 on the surfaces of the n-type GaN layer 32 and the p-type GaN layer 35 (step S26).

  Since the NGO substrate preparation process (step S21) is the same as the above-described NGO substrate preparation process (step S11), description thereof is omitted.

  As shown in FIG. 8, a GaN-based compound semiconductor is epitaxially grown on an NGO substrate 11 whose main surface on which a GaN-based compound semiconductor is grown is a (012) plane, and a buffer layer 31 is formed as a semipolar plane GaN-based compound semiconductor layer. Then, the first stacked body 24 having the n-type GaN layer 32 is formed (first stacked body forming step: step S22).

  Thereafter, as shown in FIG. 9, the NGO substrate 12 is peeled from the first laminate 24 (substrate peeling step: step S23). As a method of peeling, there is a method of peeling using, for example, an outer peripheral blade, an inner peripheral blade, a cylindrical grinding device, a wire saw, a laser, or the like, as described above. The first stacked body 24 obtained by peeling from the NGO substrate 11 is also referred to as a GaN free-standing substrate.

  Thereafter, as shown in FIG. 10, the first stacked body 24 is used as a GaN free-standing substrate, and a GaN-based compound semiconductor is epitaxially grown thereon to form a periodic layer 33, a p-type AlGaN layer 34, and a p-type GaN layer 35. The 2nd laminated body 25 containing is formed (2nd laminated body formation process: step S24).

  The stacked body 21 has a plurality of p-type or n-type GaN-based compound semiconductor layers. The first stacked body 24 includes an n-type GaN-based compound semiconductor layer, and the second stacked body 25 includes both p-type and n-type GaN-based compound semiconductor layers.

  Thereafter, as shown in FIG. 11, after a part of the surface of the p-type GaN layer 35 is protected with a resist, etching is performed until a part of the n-type GaN layer 32 is exposed (etching step: step S25).

  Thereafter, the resist is removed by sputtering, the first electrode 22 is formed on the outermost layer of the p-type GaN layer 35, and the second electrode 23 is formed on the exposed main surface of the n-type GaN layer 32 ( Electrode forming step: Step S26).

  Thereby, the light emitting device 20 as shown in FIG. 4 is obtained.

  In the method for manufacturing the light emitting device 20 according to the present embodiment, the first stacked body 24 formed on the NGO substrate 12 whose main surface is the (012) plane and the first stacked body 24 formed on the first stacked body 24. Each of the GaN-based compound semiconductor layers constituting the two stacked bodies 25 can be a semipolar surface. Therefore, according to the method for manufacturing the light-emitting device 20 according to the present embodiment, the light-emitting device 20 having a plurality of semipolar GaN-based compound semiconductor layers can be obtained using the (012) -plane NGO substrate 12. As described above, the luminous efficiency of the semipolar plane GaN-based compound semiconductor is close to the luminous efficiency of the nonpolar plane (for example, the (11-20) plane) and is higher than the luminous efficiency of the polar plane (for example, the (0001) plane). high. Therefore, since the light emitting device 20 includes the stacked body 21 formed by stacking a plurality of semipolar plane GaN-based compound semiconductor layers, the light-emitting device 20 can be a light-emitting element having high light emission efficiency using the GaN-based compound semiconductor. . As a result, when the light emitting device 20 according to the present embodiment is applied as a green LED or LD, the light emission efficiency of a green LED or LD using an InGaN layer that has conventionally been low in light emission efficiency can be significantly improved.

(Manufacturing method of other light emitting devices)
In addition, a method for manufacturing the light emitting device 30 according to the present embodiment having the stacked body 21 configured by stacking a plurality of GaN-based compound semiconductor layers on the NGO substrate 11 as illustrated in FIG. 6 will be described. FIG. 12 is a flowchart showing an example of a method for manufacturing the light emitting device 30 according to the present embodiment. As shown in FIG. 12, the method for manufacturing another configuration of the light emitting device 30 according to the present embodiment includes the following steps.
A) NGO substrate preparation process for preparing the NGO substrate 11 (step S31)
B) A GaN-based compound semiconductor is epitaxially grown on an NGO substrate 11 whose main surface on which a GaN-based compound semiconductor is grown is the (012) plane, and a semipolar GaN-based compound semiconductor layer (buffer layer 31, n-type GaN) is grown. Step of forming a laminate (step S32) for forming a laminate 21 in which a plurality of layers 32, periodic layers 33, p-type AlGaN layers 34, and p-type GaN layers 35) are laminated.
C) An etching process in which a part of the surface of the p-type GaN layer 35 is protected with a resist, and then etching is performed until a part of the n-type GaN layer 32 is exposed (step S33).
D) Electrode forming step of forming the electrodes 22 and 23 on the surfaces of the n-type GaN layer 32 and the p-type GaN layer 35 (step S34)

  Since the NGO substrate preparation step (step S31) is the same as the above-described NGO substrate preparation step (step S11), description thereof is omitted.

  As shown in FIG. 13, a GaN-based compound semiconductor is epitaxially grown on an NGO substrate 11 whose main surface on which a GaN-based compound semiconductor is grown is the (012) plane, and a plurality of semipolar plane GaN-based compound semiconductor layers are stacked. The laminated body 21 comprised is formed (step S22). The stacked body 21 is obtained by epitaxially growing a semipolar plane GaN-based compound semiconductor on the NGO substrate 11, and sequentially starting from the NGO substrate 11 side, a buffer layer 31 made of a GaN layer, an n-type GaN layer 32, and an n-type GaN / InGaN. Each of the GaN-based compound semiconductor layers of the periodic layer 33, the p-type AlGaN layer 34, and the p-type GaN layer 35 are stacked in order.

  Thereafter, as shown in FIG. 14, after a part of the surface of the p-type GaN layer 35 is protected with a resist, etching is performed until a part of the n-type GaN layer 32 is exposed (etching step: step S33). Since the etching process (step S33) is the same as the above-described etching process (step S25), description thereof is omitted.

  Thereafter, the resist is removed by sputtering, the first electrode 22 is formed on the outermost layer of the p-type GaN layer 35, and the second electrode 23 is formed on the exposed main surface of the n-type GaN layer 32 ( Electrode forming step: Step S34). Since the electrode forming step (step S34) is the same as the above-described electrode forming step (step S26), description thereof is omitted.

  Thereby, the light emitting device 30 as shown in FIG. 6 is obtained.

  In the method for manufacturing the light emitting device 30 according to this embodiment, the buffer layer 31, the n-type GaN layer 32, the periodic layer 33, and the p-type AlGaN layer formed on the NGO substrate 12 whose main surface is the (012) plane. 34 and the p-type GaN layer 35 can be semipolar planes. Therefore, according to the method for manufacturing the light emitting device 30 according to the present embodiment, the light emitting device 30 having a plurality of semipolar GaN-based compound semiconductor layers on the NGO substrate 12 from the NGO substrate 12 can be obtained. As described above, the luminous efficiency of the semipolar plane GaN-based compound semiconductor is close to the luminous efficiency of the nonpolar plane (for example, the (11-20) plane) and is higher than the luminous efficiency of the polar plane (for example, the (0001) plane). high. Therefore, since the light emitting device 30 according to the present embodiment includes the stacked body 21 configured by stacking a plurality of GaN-based compound semiconductor layers having a semipolar plane, the light-emitting element having high emission efficiency using the GaN-based compound semiconductor. It can be. As a result, when the light emitting device 30 according to the present embodiment is applied as a green LED or LD, the light emission efficiency of a green LED or LD using an InGaN layer that has conventionally been low in light emission efficiency can be significantly improved.

  The light emitting devices 20 and 30 according to the present embodiment have been described for the case where the light emitting device is used as a light emitting diode. However, the present embodiment is not particularly limited to this, and is preferably used for, for example, a field effect transistor. Can do.

  The content of the present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the following examples.

<Creation of GaN substrate>
[Example 1]
An NGO substrate with the (012) plane as the main surface was prepared. The NGO substrate is in two directions (IF direction and OF direction) perpendicular to the narrower angle (off angle) of the angles formed by the [012] direction axis of the NGO crystal of the NGO substrate and the normal line of the NGO substrate surface. Substrates changed in the range of 2 ° to 10 ° were prepared. The NGO substrate was ultrasonically washed with an acetone solution, degreased, then washed with ultrapure water and dried with a spin dryer. After putting the NGO substrate into the HVPE apparatus and cleaning the NGO substrate with the cleaning temperature of the NGO substrate being about 900 ° C., the substrate temperature of the NGO substrate during the growth of the GaN-based compound semiconductor on the NGO substrate by the HVPE method A GaN thin film (GaN-based compound semiconductor layer) was formed at about 600 ° C., using HCl and NH ₃ as source gases, an HCl supply amount of about 5 sccm, and an NH ₃ supply amount of 150 sccm. As a result, a GaN substrate having a GaN thin film formed on the NGO substrate was obtained.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that an NGO substrate having a (011) principal surface was used as the NGO substrate.

<Evaluation>
In Example 1 and Comparative Example 1, the X-ray diffraction pattern of the GaN thin film formed on the NGO substrate was measured.

[X-ray diffraction pattern of GaN thin film]
The NGO substrate on which the GaN thin film in Example 1 and Comparative Example 1 was formed was measured by setting the tilt angle Psi of the X-ray diffractometer to 0 °. The measured X-ray diffraction patterns are shown in FIGS. As a result of measuring the angle Psi of the GaN thin film X-ray diffractometer set to 0 °, as shown in FIG. 16, the GaN thin film on the NGO substrate obtained in Comparative Example 1 has a c-axis of the GaN crystal. A clear peak was observed in the vicinity of the angle (2θ = 34.5 °) corresponding to the reflection of the (0002) plane. From this, it can be said that the main surface of the NGO substrate is the (011) plane, and a GaN thin film oriented in the c-axis direction is formed on the surface. That is, when the main surface of the NGO substrate is the (011) plane, it can be said that the c-plane which is a polar surface is formed on the NGO substrate.

  On the other hand, as shown in FIG. 15, no peaks other than the (012) plane peak of the NGO crystal of the NGO substrate were confirmed from the GaN thin film on the NGO substrate obtained in Example 1.

  FIG. 17 shows an X-ray diffraction pattern obtained by measuring the NGO substrate on which the GaN thin film is formed in Example 1 with the Psi of the X-ray diffractometer set to 20 °. As shown in FIG. 17, a peak of reflection (2θ = 34.5 °) on the (0002) plane corresponding to the c-axis was observed in the direction in which Psi was shifted by 5 to 20 °. From this result, it can be said that when the main surface of the NGO substrate is the (012) plane, a semipolar plane GaN-based compound semiconductor can be grown on the NGO substrate.

  FIG. 18 is an explanatory diagram showing the relationship between the (012) plane NGO substrate and the c-plane of the GaN crystal. As shown in FIG. 18, the lattice spacing in the (100) direction of the NGO crystal and the (11-20) spacing of the GaN crystal are substantially coincident, and the c-axis of the GaN crystal is tilted around the coincident axis. It can be said that a GaN thin film is formed.

(Relationship between the off-angle of the (012) plane NGO substrate and the inclination of the c-axis of the GaN thin film)
FIG. 19 shows the relationship between the off-angle of the (012) plane NGO substrate and the inclination of the c-axis of the GaN thin film. As shown in FIG. 19, it can be said that the magnitude of the inclination of the c-axis of the GaN thin film depends on the off-angle of the (012) plane NGO substrate. Therefore, it can be said that the off angle of the (012) plane NGO substrate is preferably within ± 5 °.

(Relationship between cleaning temperature of NGO substrate and inclination of c-axis of GaN thin film)
Next, FIG. 20 shows the relationship between the cleaning temperature of the NGO substrate and the inclination of the c-axis of the GaN thin film. In FIG. 20, the thick line is an intermediate line obtained based on the value of the c-axis inclination of the GaN thin film obtained at 600 ° C., 700 ° C., 800 ° C., and 900 ° C. in the IF direction. As shown in FIG. 20, the inclination of the c-axis of the GaN thin film was greater at lower temperatures. The cleaning temperature of the NGO substrate 12 is one of the growth conditions of the GaN crystal, and the inclination of the c-axis of the GaN thin film is larger at a lower temperature. Therefore, as described above, in order to form a semipolar surface in which the c-axis of the GaN thin film is inclined by 10 ° or more, the temperature is preferably 600 ° C. or more and 700 ° C. or less.

  Therefore, it can be said that a light-emitting element having high luminous efficiency can be obtained by forming a semipolar plane GaN-based compound semiconductor layer on a (012) plane NGO substrate. Therefore, when a light emitting device is manufactured using a semipolar plane GaN substrate, the light emitting efficiency of a light emitting element such as a green LED or LD, which has conventionally been low in light emitting efficiency, can be remarkably improved. It was found that it can be suitably used as a light emitting element.

DESCRIPTION OF SYMBOLS 11 NGO board | substrate 12 Gallium nitride type compound semiconductor layer 20, 30 Light emitting device 21 Laminated body 22 1st electrode 23 2nd electrode 24 1st laminated body 25 2nd laminated body 31 Buffer layer 32 n-type GaN layer 33 Periodic layer 34 p-type AlGaN layer 35 p-type GaN layer

Claims (7)

A gallium nitride compound semiconductor is epitaxially grown on an NdGaO ₃ substrate whose principal surface on which a gallium nitride compound semiconductor is grown is a (012) plane to form a semipolar gallium nitride compound semiconductor layer. A method for producing a gallium compound semiconductor layer. In claim 1,
The NdGaO ₃ substrate of NdGaO ₃ crystal [012] axis and the NdGaO ₃ gallium nitride-based compound, characterized in that the off-angle formed between the normal of the surface of the substrate grows below ± 5.0 ° semiconductor Layer manufacturing method. In claim 1 or 2,
Before the epitaxial growth of the gallium nitride compound semiconductor, the NdGaO ₃ substrate is heat-treated at a temperature of 600 ° C. or higher and 900 ° C. or lower while supplying an inert gas into the growth furnace to clean the surface of the NdGaO ₃ substrate. After going
A method for producing a gallium nitride compound semiconductor layer, comprising growing a semipolar plane gallium nitride compound semiconductor on the NdGaO ₃ substrate. In claim 3,
A method of manufacturing a gallium nitride compound semiconductor layer, wherein a substrate temperature of the NdGaO ₃ substrate is set to 550 ° C. or more and 650 ° C. or less to grow a semipolar plane gallium nitride compound semiconductor. In any one of Claims 1 thru | or 4,
Wherein the NdGaO ₃ substrate, wherein after forming a gallium nitride-based compound semiconductor layer, the NdGaO ₃ method for producing a gallium nitride-based compound semiconductor layer, characterized in that to obtain the release to a gallium nitride-based compound semiconductor layer of the substrate. A laminate in which one or more gallium nitride compound semiconductor layers having a semipolar plane are laminated by epitaxially growing a gallium nitride compound semiconductor on an NdGaO ₃ substrate whose principal surface on which a gallium nitride compound semiconductor is grown is a (012) plane. Form the body,
The method for manufacturing a light-emitting device, wherein the gallium nitride compound semiconductor layer is p-type or n-type. A laminate in which one or more gallium nitride compound semiconductor layers having a semipolar plane are laminated by epitaxially growing a gallium nitride compound semiconductor on an NdGaO ₃ substrate whose principal surface on which a gallium nitride compound semiconductor is grown is a (012) plane. After forming the body, the laminate obtained by peeling from the NdGaO ₃ substrate was used as the first laminate,
On the first stacked body, a gallium nitride compound semiconductor is epitaxially grown to form a second stacked body in which one or more gallium nitride compound semiconductor layers having a semipolar plane are stacked,
The method for manufacturing a light-emitting device, wherein the second stacked body has a gallium nitride compound semiconductor layer of one or both of p-type and n-type.

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