TWI497766B - Method for producing semiconductor device - Google Patents

Description

Semiconductor device manufacturing method

The present invention relates to a method of fabricating a semiconductor device. More particularly, the present invention relates to a method of fabricating a semiconductor device including a p-type contact layer and a p-type electrode formed of a group III nitride semiconductor, which is intended to improve ohmic between a p-type contact layer and a p-type electrode contact.

In general, a semiconductor device includes a p-type electrode and a p-type contact layer in contact with the p-type electrode. When the contact resistance between the p-type electrode and the p-type contact layer is high, heat may be generated, and heat generation may shorten the effective life of the device. Also, when the contact resistance is high, the driving voltage of the semiconductor device rises.

In particular, in order to reduce the contact resistance between the p-type contact layer and the p-type electrode formed by the group III nitride semiconductor, the hole concentration of the p-type contact layer must be increased. However, since the deep acceptor impurity level is formed in the group III nitride semiconductor layer, difficulty is encountered in increasing the hole concentration.

Therefore, many studies have been conducted to increase the hole density. For example, Patent Document 1 discloses a technique of realizing a hole concentration of about 10 ¹⁸ /cm ³ by reducing the growth rate of the p-type contact layer.

Patent Document 1: Japanese Laid-Open Patent Application No. 2003-23179.

However, even when a p-type electrode is formed on a p-type contact layer having such a hole concentration, a preferable ohmic contact may not be obtained. At the same time, considering the work function of the layer and the electrode, difficulty is encountered in achieving an ohmic contact between the p-type contact layer and the p-type electrode formed by the group III nitride semiconductor.

The present invention has been accomplished to solve the aforementioned problems related to the prior art. Therefore, the present invention The object is to provide a method of fabricating a semiconductor device including a p-type contact layer and a p-type electrode formed of a nitride semiconductor, wherein the method is intended to improve ohmic contact between the p-type contact layer and the p-type electrode.

In a first embodiment of the present invention for solving the aforementioned problems, there is provided a method of manufacturing a semiconductor device comprising a p-type electrode, and a p formed thereon and formed of a group III nitride semiconductor a contact layer, the method comprising the step of forming a p-type contact layer, the step comprising a first sub-step of forming a first p-type contact layer by using a mixed gas of nitrogen and hydrogen as a carrier gas; and a second sub-step A second p-type contact layer is formed by using hydrogen as a carrier gas.

In the semiconductor device manufactured by the semiconductor device manufacturing method, a preferable ohmic contact is achieved between the p-type contact layer and the p-type electrode; that is, a low contact resistance is achieved therebetween. Therefore, power consumption can be reduced, and the total amount of heat generation is also reduced.

A second embodiment of the present invention is directed to a specific embodiment of a method of fabricating a semiconductor device, wherein the first substep uses a molar ratio of nitrogen to the overall carrier gas (hereinafter the ratio can be expressed as "nitrogen mole fraction") It is 40% to 80% of carrier gas. The use of this carrier gas achieves the formation of a first p-type contact layer with reduced lattice defects. Therefore, the first p-type contact layer thus formed exhibits a more reduced resistivity. More preferably, the nitrogen molar fraction is from 50% to 75%. Most preferably, the nitrogen molar fraction is from 55% to 70%.

A third embodiment of the present invention is directed to a specific embodiment of a method of fabricating a semiconductor device in which an annealing step for reducing the resistance of a p-type contact layer is not performed. The omission of this annealing step shortens the cycle time and improves productivity.

A fourth embodiment of the present invention is directed to a specific embodiment of a method of fabricating a semiconductor device, further comprising the step of cooling a layered product comprising a p-type contact layer in a nitrogen atmosphere after the second sub-step. Cooling of the layered product in a nitrogen atmosphere prevents recombination of hydrogen by the acceptor impurities.

A fifth embodiment of the present invention is directed to a specific embodiment of a method of fabricating a semiconductor device, wherein the second sub-step forms a second p-type contact layer having a thickness of 10 Å to 100 Å. When the thickness of the second p-type contact layer falls within the above range, a lattice defect is appropriately formed in the layer. By tunneling, the carrier easily passes through the potential barrier through the lattice defects thus formed. More preferably, the second p-type contact layer has a thickness of from 20 Å to 90 Å. Even more preferably, the second p-type contact The thickness of the layer is 30 Å to 70 Å.

A sixth embodiment of the present invention is directed to a specific embodiment of a method of fabricating a semiconductor device, wherein during the forming of the second p-type contact layer in the second sub-step, the second p-type contact layer is higher than the first The concentration of the Mg concentration of the p-type contact layer is doped with Mg, and the Mg concentration of the second p-type contact layer is adjusted to 1 × 10 ²⁰ /cm ³ to 1 × 10 ²² /cm ³ . More preferably, the Mg concentration is adjusted to 2 × 10 ²⁰ /cm ³ to 9 × 10 ²¹ /cm ³ . More preferably, the Mg concentration is adjusted to 5 × 10 ²⁰ /cm ³ to 8 × 10 ²¹ /cm ³ . This is because when the Mg concentration of the second p-type contact layer falls within the above range, a larger amount of lattice defects can be formed in the layer. Therefore, after the activation of Mg, electrons move smoothly between the p-type electrode and the p-type contact layer.

According to the present invention, there is provided a method of fabricating a semiconductor device comprising a p-type contact layer and a p-type electrode formed of a nitride semiconductor, wherein the method is intended to improve ohmic contact between the p-type contact layer and the p-type electrode.

10‧‧‧Sapphire substrate

20‧‧‧Low temperature buffer layer

30‧‧‧N type contact layer

40‧‧‧N type ESD layer

50‧‧‧N type SL layer

60‧‧‧MQW layer

70‧‧‧P type coating

80‧‧‧P type contact layer

90‧‧‧Layered products

100‧‧‧Lighting device

N1‧‧‧N type electrode

P1‧‧‧P type electrode

The other objects, features, and advantages of the present invention will become more apparent upon consideration of 1 schematically shows a layered structure of a semiconductor device according to an embodiment; FIGS. 2A to 2C show a method of fabricating a semiconductor device according to an embodiment (Part 1); and FIG. 3 shows a method of manufacturing a semiconductor device according to an embodiment (Part 2) FIG. 4 is a graph showing the hole concentration of the first p-type contact layer of the light-emitting device manufactured by the semiconductor device manufacturing method according to the embodiment; FIG. 5 is a view showing the light-emitting device manufactured by the semiconductor device manufacturing method according to the embodiment; a graph of hole mobility in the first p-type contact layer; FIG. 6 is a graph showing resistivity in the first p-type contact layer of the light-emitting device manufactured by the semiconductor device manufacturing method according to the embodiment; FIG. a graph of the percentage of activation in the first p-type contact layer of the light-emitting device manufactured by the semiconductor device manufacturing method according to the embodiment; and FIG. 8 is shown in accordance with an embodiment The method of manufacturing a light emitting semiconductor device fabricated loaded An output comparison chart between conventional light-emitting devices is placed.

Specific embodiments of the present invention will be described next with reference to the drawings by taking a case of manufacturing a light emitting device. However, the invention is not limited to the embodiment. That is, the present invention can be applied to different semiconductor devices, including a transistor such as a field effect modified transistor (FEMT), a photodetector, and a light emitting device such as an LED or a laser diode. Needless to say, the structure of each layer forming the light-emitting device may be different from that exemplified in the embodiments described below. The thickness of each layer schematically shown in the drawings does not correspond to its actual value.

Example Semiconductor device

A light-emitting device 100 manufactured via the semiconductor device manufacturing method according to the present embodiment will now be described with reference to FIG. The light-emitting device 100 is a semiconductor device formed of a group III nitride semiconductor. As shown in FIG. 1, the light emitting device 100 includes a sapphire substrate 10, a low temperature buffer layer 20, an n-type contact layer 30, an n-type electrostatic discharge (ESD) layer 40, and an n-type superlattice (SL). The layer 50, a multiple quantum well (MQW) layer 60, a p-type cladding layer 70, and a p-type contact layer 80, which are used as light sources, are formed on the sapphire substrate 10 in this order. The n-type electrode N1 is formed on the n-type contact layer 30. The p-type electrode P1 is formed on the p-type contact layer 80.

The individual layers described above are formed on one surface of the sapphire substrate 10 via metal-organic chemical vapor deposition (MOCVD). This surface of the sapphire substrate 10 may be protruded for the purpose of improving the performance of light extraction. The sapphire substrate may be replaced by another growth substrate such as SiC, ZnO, Si or GaN. The low temperature buffer layer 20 is provided to transfer the crystallinity of the sapphire substrate 10 to a layer formed on the buffer layer 20. Exemplary materials for the low temperature buffer layer 20 include AlN and GaN.

The n-type contact layer 30 is actually in contact with the n-type electrode N1. The n-type contact layer 30 is formed of GaN doped with Si. The Si concentration of the layer 30 is 1 × 10 ¹⁸ /cm ³ or higher. The n-type contact layer 30 may be formed of a plurality of layers having different carrier concentrations for the purpose of improving the ohmic contact between the n-type contact layer 30 and the n-type electrode.

The n-type ESD layer 40 is provided to improve electrostatic discharge; that is, to prevent electrostatic discharge of each semiconductor layer. The n-type ESD layer 40 has a layered structure including an undoped GaN layer and a Si-doped GaN layer. Preferably, the Si doping is performed to obtain a carrier concentration of 1 × 10 ¹⁸ /cm ³ or higher.

The n-type SL layer 50 has a superlattice structure for relieving stress applied to the MQW layer 60. The n-type SL layer 50 is formed by alternately depositing a GaN layer and an InGaN layer. In addition to these layers, an n-GaN layer may be deposited. More preferably, the n-GaN layer is in contact with the MQW layer 60. The number of layer units forming the n-type SL layer 50 is 10 to 20. The n-type SL layer 50 has an overall thickness of 60 nm to 80 nm.

The MQW layer 60 is a light-emitting layer that emits light by recombination of electrons and holes. Therefore, the MQW layer 60 is formed by alternately depositing a well layer having a small energy gap and a barrier layer having a large energy gap. The well layer may be formed of InGaN, and the barrier layer may be formed of AlGaN. Alternatively, the well layer may be formed of GaN, and the barrier layer may be formed of AlGaN. Alternatively, MQW layer 60 may be formed from any combination of these layers; for example, layer 60 may be formed of repeating layer units, each layer unit comprising four or more layers.

The p-type cladding layer 70 is provided to prevent electrons from diffusing to the p-type contact layer 80. The p-type cladding layer 70 is formed by alternately depositing layer units including a p-InGaN layer and layer units including a p-AlGaN layer. The number of repeated layer units is 12. The number of repeating layer units can range from 3 to 50.

The p-type contact layer 80 includes a first p-type contact layer 81 and a second p-type contact layer 82. Each of these layers is formed of Mg-doped p-GaN. The second p-type contact layer 82 is actually in contact with the p-type electrode P1. Therefore, in the light emitting device 100, the second p-type contact layer 82 is positioned on the side opposite to the sapphire substrate 10 side. The first p-type contact layer 81 is tied below the second p-type contact layer 82.

The first p-type contact layer 81 is doped with Mg at a concentration of 1 × 10 ¹⁹ /cm ³ to 1 × 10 ²⁰ /cm ³ . When the Mg concentration falls within this range, the high hole concentration is achieved without deteriorating the crystallinity. The second p-type contact layer 82 is doped with Mg at a concentration of 1 × 10 ²⁰ /cm ³ to 1 × 10 ²² /cm ³ . That is, the second p-type contact layer 82 is doped with Mg at a concentration higher than the Mg concentration of the first p-type contact layer 81.

The second p-type contact layer 82 has a thickness of 10 Å to 100 Å. Therefore, the thickness of the second p-type contact layer 82 is sufficiently thin. As described below, the carrier gas used to form the second p-type contact layer 82 contains only hydrogen (ie, the carrier gas does not contain nitrogen). Thus, the second p-type contact layer 82 exhibits poor crystallinity. Therefore, a very thin Schottky barrier is formed between the p-type electrode P1 and the second p-type contact layer 82.

Therefore, the hole is easily moved from the p-type electrode P1 to the second p-type contact layer 82. That is, the hole from the p-type electrode P1 easily passes through the Schöne barrier to the second p-type contact layer 82. Therefore, a better ohmic contact is achieved between the p-type electrode P1 and the p-type contact layer 80.

2. Semiconductor device manufacturing method

In the semiconductor device manufacturing method according to the present embodiment, the aforementioned individual layers are grown by metal-organic chemical vapor deposition (MOCVD). The attribute characteristics of the semiconductor device manufacturing method according to the present embodiment exist in the step of forming the p-type contact layer 80. The steps of the method will be described next with reference to Figures 2 and 3.

The carrier gas used in the method is a mixed gas of hydrogen (H ₂ , hydrogen), nitrogen (N ₂ , nitrogen), or hydrogen plus nitrogen (H ₂ + N ₂ ). Ammonia gas (NH ₃ ) is used as a nitrogen source. Trimethylgallium (Ga(CH ₃ ) ₃ , trimethylgallium, hereinafter referred to as "TMG") is used as a gallium source. Trimethyl indium (In(CH ₃ ) ₃ , trimethylindium, hereinafter referred to as "TMI") is used as an indium source. Trimethylaluminum (Al(CH ₃ ) ₃ , trimethylaluminum, hereinafter referred to as "TMA") is used as an aluminum source. Silicone (SiH ₄ , silane) is used as an n-type dopant gas. Magnesium cyclopentadienide (Mg(C ₅ H ₅ ) ₂ , cyclopentadienylmagnesium, hereinafter referred to as "Cp ₂ Mg") is used as a p-type doping gas.

2-1. Step of forming a low temperature buffer layer

A sapphire substrate 10 is provided in this embodiment, and the sapphire substrate 10 is placed in a MOVCD furnace. Next, the sapphire substrate 10 is cleaned in a hydrogen atmosphere to further remove deposits from the surface of the sapphire substrate 10. Then, the substrate temperature is raised to 400 ° C, and the AlN low temperature buffer layer 20 is formed on the sapphire substrate 10.

2-2. Step of forming an n-type contact layer

Next, an n-type contact layer 30 is formed over the low temperature buffer layer 20 (see FIG. 2A). Then, the substrate temperature was raised to 1,100 ° C under a flow of hydrogen (carrier gas) and ammonia gas. After the substrate temperature has reached 1,100 ° C, TMG, ammonia gas, and decane gas (i.e., impurity gas) are supplied to further form an n-type contact layer 30 of n-GaN having a Si concentration of 4.5 × 10 ¹⁸ /cm ³ .

2-3. Steps of forming an n-type ESD layer

Next, an n-type ESD layer 40 is formed on the n-type contact layer 30. The substrate temperature was lowered to 900 ° C, and a layered structure including an undoped GaN layer and an Si-doped n-GaN layer was formed. In this case, the growth temperature is preferably adjusted to 800 to 950 °C. The n-GaN layer preferably has a characteristic value defined by a product of a cesium atom concentration (atom/cm ³ ) and a thickness (nm): 0.9 × 10 ²⁰ to 3.6 × 10 ²⁰ (atom ‧ nm / cm ³ ) .

2-4. Step of forming an n-type SL layer

Next, an n-type SL layer 50 is formed on the n-type ESD layer 40. The n-type SL layer 50 is formed by alternately depositing an InGaN layer having a thickness of 2.5 nm and a Si-doped n-GaN layer having a thickness of 2.5 nm and doped with Si. Specifically, the n-type SL layer 50 is formed by periodically depositing 15 combined layer units each including an InGaN layer and a Si-doped n-GaN layer. The InGaN layer was formed under the supply of decane gas, TMG, TMI, and ammonia while maintaining the substrate temperature at 830 °C. The n-GaN layer was formed under the supply of decane gas, TMG, and ammonia while maintaining the substrate temperature at 830 °C. Thus, the layered structure shown in Fig. 2B is formed.

2-5. Step of forming a light-emitting layer

Next, the MQW layer 60 is formed on the n-type SL layer 50. The MQW layer 60 has a structure in which an InGaN layer and an AlGaN layer are alternately deposited in a repeated manner. The InGaN layer is grown at a growth temperature of 750 to 800 °C. The material gases (i.e., TMI, TMG, and ammonia) are supplied as a growth of the InGaN layer. The In composition ratio is 0.05 to 0.15%. The crystal layer grown in this way has a thickness of 1 to 4 nm.

The AlGaN layer is grown at a growth temperature of 850 to 950 °C. The material gases (ie, TMA, TMG, and ammonia) are supplied as a grown AlGaN layer. The crystal layer grown in this way has 1 Thickness to 6 nm. Five layers of InGaN layer and five layers of AlGaN layer are alternately deposited. The number of InGaN layers or AlGaN layers is preferably from about 3 to about 7.

2-6. Step of forming a p-type cladding layer

Next, a p-type cladding layer 70 is formed on the MQW layer 60. The p-type cladding layer 70 has a structure in which a p-InGaN layer and a p-AlGaN layer are alternately deposited in a repeated manner. A p-InGaN layer (p-In _0.05 Ga _0.95 N layer) having a thickness of 1.7 nm was formed under the supply of CP ₂ Mg, TMI, TMG, and ammonia while maintaining the substrate temperature at 855 ° C.

The p-AlGaN layer having a thickness of 3.0 nm was formed under the supply of CP ₂ Mg, TMA, TMG, and ammonia while maintaining the substrate temperature at 855 ° C. Thus, the layered structure shown in Fig. 2C is formed.

2-7. Step of forming a p-type contact layer 2-7-1. Step of forming a first p-type contact layer

Next, a first p-type contact layer 81 is formed on the p-type cladding layer 70 (see FIG. 3). A mixed gas system of nitrogen and hydrogen is used as a carrier gas.

The advantage of the presence of hydrogen increases the migration of constituent atoms. Therefore, the crystal quality is improved and the surface smoothness of the layer is also improved. However, a hydrogen atom enters the crystal and binds to Mg. This combination prevents the activation of Mg. Therefore, the hole concentration in the first p-type contact layer 82 does not increase.

Conversely, nitrogen can prevent nitrogen atoms from being removed from the crystal by inhibiting decomposition of the crystal. However, nitrogen may cause deterioration in crystallinity. Therefore, the nitrogen molar fraction of the carrier gas must be adjusted to fall within the most desirable range.

The nitrogen molar fraction of the carrier gas (i.e., the mixing ratio (N ₂ /(H ₂ + N ₂ ))) is preferably from 40% to 80%. The mixing ratio is more preferably from 50% to 75%. Specific values for this ratio will be described below. As described below, when the mixing ratio (N ₂ /(H ₂ +N ₂ )) is less than 40%, a sufficient hole concentration cannot be obtained, and when the mixing ratio (N ₂ /(H ₂ +N ₂ )) exceeds At 80%, the surface may become rough and pits may increase.

The crystal growth temperature was adjusted to 900 ° C to 1,050 ° C. This is because when the temperature is excessively low, the crystal quality of GaN is impaired, and when the temperature exceeds 1,050 ° C, the material gas is in individual The raw material gas reacts before it reaches the sapphire substrate 10.

The first p-type contact layer 81 is doped with Mg at a concentration of 1 × 10 ¹⁹ /cm ³ to 1 × 10 ²⁰ /cm ³ . This is because when the doping concentration of Mg is 1 × 10 ²⁰ / cm ³ or less, more lattice defects can not be formed based on the first p-type contact layer 81. The first p-type contact layer 81 is formed to have a thickness of 100 Å to 1,000 Å.

2-7-2. Step of forming a second p-type contact layer

Next, a second p-type contact layer 82 is formed on the first p-type contact layer 81. In order to intentionally form a large number of lattice defects in the second p-type contact layer 82, only hydrogen gas is used as the carrier gas. Therefore, the supply of nitrogen gas is stopped, and only hydrogen gas is supplied as the carrier gas. That is, the carrier gas used does not contain nitrogen. However, since the aforementioned layer forming step is continuously performed inside the MOCVD furnace, nitrogen may remain in the atmosphere of the furnace.

The crystal growth temperature was adjusted to 800 ° C to 1,050 ° C. This is because when the growth temperature is lower than 800 ° C, the crystal quality of GaN is impaired, and when the growth temperature exceeds 1,050 ° C, the reaction may be carried out in the atmosphere of the reaction furnace before ammonia, Ga, Mg, etc. arrive at the sapphire substrate 10. .

The second p-type contact layer 82 is doped with Mg at a concentration of 1 × 10 ²⁰ /cm ³ to 1 × 10 ²² /cm ³ . This is because when the doping Mg concentration is 1 × 10 ²⁰ /cm ³ or higher, lattice defects are more likely to be formed in the produced semiconductor layer.

The second p-type contact layer 82 is formed to have a thickness of 10 Å to 100 Å. This is because when the thickness is less than 10 Å, difficulties are encountered in forming lattice defects. Since GaN has a lattice constant of 5.185 Å in the c-axis direction, lattice defects are easily formed when the layer thickness corresponds to the thickness of two or more GaN molecular layers. However, the greater the thickness of the layer having lattice defects, the higher its resistance. Therefore, the thickness of the second p-type contact layer 82 is preferably 100 Å or less, more preferably 20 Å to 90 Å, still more preferably 30 Å to 70 Å.

2-8. Cooling step

Next, the MOCVD furnace was cooled to ambient temperature in a nitrogen atmosphere. Specifically, the layered product 90 shown in FIG. 3 is cooled in a nitrogen atmosphere to prevent recombination of desorbed hydrogen into the layered product 90.

2-9. Electrode formation steps

Next, dry etching is performed from the upper surface of the p-type contact layer 80 to further form a trench extending to the intermediate portion of the n-type contact layer 30. Then, a p-type electrode P1 is formed on the p-type contact layer 80. The p-type electrode P1 is formed by depositing on the p-type contact layer 80 in the order of a Ni layer, an Au layer, and then an Al layer. Any of these metals can be replaced by ITO. Further, a Ni/Au wiring electrode can be formed on the ITO electrode. Alternatively, Ag or Rh can be used. The n-type electrode N1 is formed on the exposed portion of the n-type contact layer 30. The n-type electrode N1 is formed by depositing on the n-type contact layer 30 in the order of a Ni layer and then an Au layer. Alternatively, the n-type electrode N1 can be formed by continuously depositing a Ti layer and an Al layer on the n-type contact layer 30.

2-10. Annealing step

Next, in order to activate Mg doped thereon, the layered product 90 is subjected to heat treatment (annealing) in a nitrogen atmosphere. This annealing step can be performed before the electrode forming step or before the cooling step. Thus, the light emitting device 100 shown in Fig. 1 is fabricated.

3. Manufacturing semiconductor device

In the light emitting device 100 according to the present embodiment, the p-type contact layer 80 includes the first p-type contact layer 81 and the second p-type contact layer 82. By virtue of the existence of the second p-type contact layer 82, the Schindler barrier between the p-type contact layer 80 and the p-type electrode P1 has a small thickness. Therefore, high hole conductivity is achieved between the p-type contact layer 80 and the p-type electrode P1.

The second p-type contact layer 82 has a number of lattice defects. Needless to say, the number of lattice defects in the second p-type contact layer 82 is larger than that in the first p-type contact layer 81. Therefore, high hole conductivity is achieved between the p-type electrode P1 and the second p-type contact layer 82.

A case in which the second p-type contact layer 82 is not provided will now be described. When the p-type electrode P1 is in contact with the first p-type contact layer 81, the driving voltage Vf becomes higher than in the case where the second p-type contact layer 82 exists. It is understood that a relatively thick Schottky barrier is formed between the first p-type contact layer 81 and the p-type electrode P1.

Conversely, when the second P-type contact layer 82 is disposed, the thickness of the Schindler barrier is reduced; That is, the hole can be easily moved between the p-type electrode P1 and the p-type contact layer 80. As described above, the number of lattice defects in the second p-type contact layer 82 is larger than that in the first p-type contact layer 81. Therefore, the hole can be more easily moved between the p-type electrode P1 and the p-type contact layer 80. Therefore, the light-emitting device 100 according to the present embodiment exhibits a low resistivity.

4. Experimental results

Next, the experimental results performed on the light-emitting device 100 according to the present embodiment will be described. The physical value determined by changing the nitrogen mixture ratio in the carrier gas for forming the first p-type contact layer 81 will now be described.

4-1. Hole concentration

4 is a graph showing the hole concentration of the first p-type contact layer 81 in relation to the nitrogen mixture ratio (N ₂ /(H ₂ +N ₂ )). In FIG. 4, the white symbol corresponds to a value in the case where annealing is not performed, and the black symbol corresponds to a value in the case where annealing is performed. The same applies to Figures 5 and 6.

As shown in FIG. 4, roughly, in the case where annealing is performed, the hole concentration is higher than in the case where annealing is not performed. That is, in the case where annealing is performed, the hole concentration is sufficiently high regardless of the nitrogen mixture ratio. Specifically, a hole concentration of about 5 × 10 ¹⁶ /cm ³ to about 6 × 10 ¹⁶ /cm ³ is achieved.

Conversely, in the case where annealing is not performed, the hole concentration is increased by increasing the nitrogen concentration. In the case where the nitrogen mixture ratio was adjusted to 44%, a hole concentration of about 2 × 10 ¹⁶ /cm ³ to 3 × 10 ¹⁶ /cm ³ was reached even when annealing was not performed. That is, the hole concentration is about 1/2 of the case in which annealing is performed. Thus, it is understood that the hydrogen atoms are bonded to half of the Mg atoms before annealing.

In the case where the nitrogen mixture ratio was adjusted to 66%, a hole concentration of about 5 × 10 ¹⁶ /cm ^{3 was} reached even when annealing was not performed. That is, the hole concentration is almost equal to the case in which the annealing is performed. It is therefore understood that virtually no hydrogen atoms are bonded to the Mg atoms even before annealing. Therefore, when the nitrogen mixture ratio is adjusted to 44% or 66%, a sufficiently high hole concentration is obtained.

4-2. Hole mobility

Fig. 5 is a graph showing the hole mobility in the first p-type contact layer 81 in relation to the nitrogen mixture ratio (N ₂ /(H ₂ + N ₂ )). As shown in FIG. 5, variation in less hole mobility was observed between the case where annealing was performed and the case where annealing was not performed. As the nitrogen concentration increases, the hole mobility improves; that is, the lattice defects decrease. This indication forms a p-GaN layer with good crystal quality.

In the case where the nitrogen mixture ratio was adjusted to 22%, a hole mobility of about 2 cm ² /V‧s was obtained when annealing was not performed, and about 3 cm ² /V‧s was obtained when annealing was performed. Hole mobility. In the case where the nitrogen mixture ratio was adjusted to 44%, a hole mobility of 4 cm ² /V‧s was obtained regardless of whether or not annealing was performed. In the case where the nitrogen mixture ratio was adjusted to 66%, a hole mobility of 7 to 8 cm ² /V‧s was obtained regardless of whether or not annealing was performed.

Therefore, annealing causes a slight difference in hole mobility. Especially when the nitrogen mixing ratio is adjusted to 44% or 66%, annealing does not actually cause a difference in hole mobility. Thus, a p-GaN layer having good hole conductivity can be formed.

4-3. Resistivity

Fig. 6 is a graph showing the resistivity of the first p-type contact layer 81 in relation to the nitrogen mixture ratio (N ₂ /(H ₂ + N ₂ )). As shown in FIG. 6, roughly, the higher the nitrogen mixing ratio, the lower the electrical resistivity. Understandably, this decrease in resistivity is due to the fact that the crystal quality is improved, and the resistance component due to lattice defects is reduced. This is evidenced by the improvement in hole mobility.

In the case where the nitrogen mixing ratio is adjusted to 22%, the unannealed first p-type contact layer 81 exhibits a resistivity of about 110 Ω ‧ cm, and the annealed first p-type contact layer 81 exhibits about 40 to about 50 Ω The resistivity of cm. The resistivity of the unannealed first p-type contact layer 81 is about twice that of the annealed first p-type contact layer 81. That is, the hydrogen atoms are still bonded to half of the Mg atoms before annealing.

In the case where the nitrogen mixture ratio is adjusted to 44%, the unannealed first p-type contact layer 81 exhibits a resistivity of about 40 to about 70 Ω ‧ cm, which is almost equal to the case of a nitrogen mixture ratio of 22% The first p-type contact layer 81 is annealed. In the case where the nitrogen mixture ratio was adjusted to 44%, the annealed first p-type contact layer 81 exhibited a resistivity of about 20 Ω ‧ cm. That is, not refunded The resistivity of the first p-type contact layer 81 of the fire is about twice that of the annealed first p-type contact layer 81.

In the case where the nitrogen mixture ratio was adjusted to 66%, the unannealed first p-type contact layer 81 exhibited a resistivity of about 15 Ω ‧ cm. In the case where the nitrogen mixture ratio was adjusted to 66%, the annealed first p-type contact layer 81 exhibited a resistivity of about 12 Ω ‧ cm. That is, the resistivity of these layers is almost equal to each other regardless of whether or not annealing is performed.

The resistivity (i.e., 15 Ω ‧ cm) of the non-annealed first p-type contact layer 81 in the case of a 66% nitrogen mixture ratio is sufficiently lower than the first p-type annealed in the case of a nitrogen mixture ratio of 22% The resistivity of the contact layer 81 (i.e., 40 to 50 Ω ‧ cm). Therefore, when the first p-type contact layer 81 is formed by using a mixed gas of nitrogen and hydrogen as a carrier gas, the electric resistance of the layer is very effectively reduced.

4-4. Activation percentage

Fig. 7 is a graph showing the percentage of activation of the first p-type contact layer 81 in relation to the nitrogen mixture ratio (N ₂ /(H ₂ + N ₂ )). In this chart, all values correspond to the case in which annealing is performed.

As shown in Figure 7, in the case where nitrogen was not mixed into the carrier gas (i.e., only hydrogen was used), the first p-type contact layer 81 exhibited a percent activation of about 0.12%. As the nitrogen mixing ratio increases, the initial percentage of activation decreases. When the nitrogen mixing ratio was 22%, the first p-type contact layer 81 showed a percentage of activation of about 0.07%.

However, as the nitrogen mixing ratio is further increased, the percentage of activation also increases. When the nitrogen mixing ratio is 35% or about, the percentage of activation is almost equal to the case where the nitrogen mixing ratio is 0%. A sufficiently high percentage of activation is achieved when the nitrogen mixing ratio is 40% or more.

When the nitrogen mixing ratio was adjusted to 44%, the first p-type contact layer 81 showed an activation percentage of about 0.14%. When the nitrogen mixing ratio was adjusted to 66%, the first p-type contact layer 81 showed an activation percentage of about 0.21%, which was a sufficiently high value.

4-5. Light intensity

8 is a view showing a case where the first p-type contact layer 81 is formed by using hydrogen gas (conventional case), and a first p-type contact layer 81 thereof is a mixed gas using nitrogen gas and hydrogen gas (nitrogen mixture ratio: 66%) A graph comparing the relative light intensities of the light-emitting devices between the cases formed (this embodiment). show on The result in Fig. 8 corresponds to the case in which annealing is performed. In Fig. 8, the vertical axis corresponds to the relative light intensity of the light intensity according to the conventional case. Needless to say, the relative light intensity of the conventional situation corresponds to 100%.

As shown in FIG. 8, in the case where the first p-type contact layer 81 is formed by using a mixed gas of nitrogen gas and hydrogen gas (nitrogen mixture ratio: 66%) as a carrier gas, the light output system is higher than conventionally. In the case of about 10%. As described above, this is because the light-emitting device manufactured by using the mixed gas as the carrier gas exhibits better resistivity, hole concentration, hole mobility, and percentage of activation.

In these experiments, the best results were obtained when the nitrogen mixing ratio was adjusted to 66%, and good results were obtained even when the nitrogen mixture ratio was adjusted to 44%. Therefore, it is understood that the present invention is also applicable to the case where the nitrogen mixing ratio is higher than this range (i.e., the nitrogen mixing ratio is 80 or less), except in the case where the nitrogen mixing ratio is from 44% to 66%. . However, when the nitrogen mixing ratio is high, there may occur a case where the surface roughness or pits increase. Thus, nitrogen mixing is preferably from 50% to 70%. It is understood that the nitrogen mixing ratio is more preferably from 55% to 70%.

5. Modify 5-1. Omission of the annealing step

In the present embodiment, annealing (heat treatment) is performed after the p-type electrode P1 and the n-type electrode N1 are formed on the layered structure 90. However, as shown in FIGS. 4 to 6, annealing is not necessarily performed. For example, according to the hole concentration (see Figure 4), hole mobility (see Figure 5), resistivity (see Figure 6), and percent activation (see Figure 7), even when annealing is not performed, A light-emitting device capable of exhibiting a relatively low resistivity can be manufactured. Therefore, a manufacturing step can be omitted; that is, the light-emitting device is manufactured with improved productivity.

5-2. Material of p-type contact layer

In the present embodiment, each of the first p-type contact layer 81 and the second p-type contact layer 82 is formed of p-GaN. However, layers 81 and 82 may be formed by p-InGaN instead of p-GaN. Since the use of p-GaN achieves an improvement in ohmic contact, similar results are inevitably obtained even when p-InGaN having an energy gap smaller than that of p-GaN is used.

In a specific case, the first p-type contact layer 81 is formed of p-GaN, and the second p-type contact layer 82 is formed of p-InGaN. Alternatively, the first p-type contact layer 81 may be formed of p-InGaN, and the second p-type contact layer 82 may also be formed of p-InGaN. In this case, the In composition ratio of the second p-type contact layer 82 is preferably adjusted to be higher than that of the first p-type contact layer 81.

6. Summary

As described in detail above, in the method of manufacturing the light-emitting device 100 according to the present embodiment, the first p-type contact layer 81 is formed via a first p-type contact layer forming step using a mixed gas of nitrogen and hydrogen as a carrier gas, And the second p-type contact layer 82 is formed via a second p-type contact layer forming step using hydrogen as a carrier gas.

Therefore, according to the method of manufacturing the group III nitride semiconductor light-emitting device, the hole mobility can be improved in the p-type contact layer 80, and the contact resistance between the p-type contact layer 80 and the p-type electrode P1 can be reduced.

This embodiment is merely illustrative, and should not be construed as limiting the invention to the embodiment. Therefore, it is to be understood that various modifications and changes can be made in the present invention without departing from the scope of the invention. The layered structure 90 shown in Fig. 3 is used in this embodiment. However, the structure of the layered product is not necessarily limited to that shown in FIG. For example, any layered structure may be selected, or any number of layer units may be determined in order to form the layers. Needless to say, the composition of the layers other than the p-type contact layer 80 may be different from that described in the embodiment. Crystal growth is not necessarily performed via metal-organic chemical vapor deposition (MOCVD), and any other crystal growth method using a carrier gas can be used.

10‧‧‧Sapphire substrate

20‧‧‧Low temperature buffer layer

30‧‧‧N type contact layer

40‧‧‧N type ESD layer

50‧‧‧N type SL layer

60‧‧‧MQW layer

70‧‧‧P type coating

80‧‧‧P type contact layer

100‧‧‧Lighting device

N1‧‧‧N type electrode

P1‧‧‧P type electrode

Claims (3)

A method of fabricating a semiconductor device, the method comprising the steps of: forming a light-emitting layer, forming a p-type cladding layer on the light-emitting layer, forming a p-type contact layer on the p-type cladding layer, and forming the p-type contact layer on the p-type contact layer Forming a p-type electrode on the layer; wherein the step of forming the p-type contact layer comprises: a first sub-step of forming a first p-type contact layer on the p-type cladding layer; and a second sub-step Forming a second p-type contact layer on the first p-type contact layer; in the first sub-step, using a mixed gas of nitrogen and hydrogen as the carrier gas, and the molar fraction of nitrogen to the overall carrier gas is 50% to 75%, the first p-type contact layer is doped with Mg to a concentration of 1×10 ¹⁹ /cm ³ to 1×10 ²⁰ /cm ³ , and the thickness of the first p-type contact layer is 100 Å to 1000 Å; In the two sub-steps, hydrogen is used as a carrier gas, and the second p-type contact layer is doped with Mg to a concentration higher than a Mg concentration of the first p-type contact layer, and the Mg concentration of the second p-type contact layer is adjusted. The thickness of the second p-type contact layer is from 20 Å to 90 Å to 2 × 10 ²⁰ /cm ³ to 9 × 10 ²¹ /cm ³ . The method of manufacturing a semiconductor device according to claim 1, wherein an annealing step for reducing the resistance of the p-type contact layer is performed, and a hole concentration of the p-type contact layer is adjusted to 5 × 10 ¹⁶ /cm ³ to 6 ×10 ¹⁶ /cm ³ . A method of manufacturing a semiconductor device according to claim 1, wherein an annealing step for reducing the resistance of the p-type contact layer is not performed, and a hole concentration of the p-type contact layer is adjusted to 2 × 10 ¹⁶ /cm ³ to 3 × 10 ¹⁶ /cm ³ , the resistivity of the p-type contact layer was adjusted to 40 to 70 Ω ‧ cm.