Group iii nitride substrate

Abstract

Provided is a Group III nitride substrate having a high carrier concentration, low dislocation density, and low resistance. The Group III nitride substrate has, in a polished plane, a first region having a first impurity concentration and a second region having a second impurity concentration lower than the first impurity concentration, and a first dislocation density of the first region is lower than a second dislocation density of the second region.

Description

Technical Field

[0001] This invention relates to a group III nitride substrate. Background Technology

[0002] Previously, vertical GaN power devices required GaN substrates with low resistance and low dislocation. For example, when fabricating n-type low-resistance GaN substrates, operations were performed to increase the carrier concentration by increasing the amount of Si and O atoms incorporated (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-132558 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, when the carrier concentration reaches 1×10 20 / cm 3 At such high concentrations, problems such as decreased crystallinity and increased dislocation defects may sometimes occur.

[0008] The object of the present invention is to provide a group III nitride substrate that achieves high carrier concentration, low dislocation and low resistance.

[0009] Methods for solving problems

[0010] The group III nitride substrate of the present invention has, in its polished surface, a first region displaying a first impurity concentration and a second region displaying a second impurity concentration lower than the first impurity concentration.

[0011] The first dislocation density in the first region is lower than the second dislocation density in the second region.

[0012] Invention Effects

[0013] The group III nitride substrate of the present invention has low dislocation density and low resistance, which can suppress leakage in the second region with high dislocation density during device formation and improve the insulation withstand voltage. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the group III nitride substrate of Embodiment 1 as viewed from the m-side.

[0015] Figure 2 This is a cross-sectional view of the group III nitride substrate of Embodiment 1 as seen from side a.

[0016] Figure 3 This is a scanning electron microscope image showing the distribution of corrosion pits on the surface of the group III nitride substrate of Embodiment 1 after surface grinding and etching.

[0017] Figure 4 It means Figure 3 Cathodic emission (CL) image of surface dislocations observed from the c-axis on a group III nitride substrate.

[0018] Figure 5 It represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate, based on the analytical range of secondary ion mass spectrometry.

[0019] Figure 6 yes Figure 5 The range of microscopic images analyzed.

[0020] Figure 7 It is aimed at Figure 5 The analytical range will be represented by a graph showing the concentration of oxygen obtained by secondary ion mass spectrometry.

[0021] Figure 8 It is aimed at Figure 5 The analytical range will be represented by a graph showing the concentration of Si obtained by secondary ion mass spectrometry.

[0022] Figure 9 This represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate with an OVPE-GaN layer thickness of 50 μm.

[0023] Figure 10 This represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate with an OVPE-GaN layer thickness of 200 μm.

[0024] Figure 11 This represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate with an OVPE-GaN layer thickness of 300 μm.

[0025] Figure 12 This is a graph showing the relationship between the thickness of the OVPE-GaN layer and the dislocation density.

[0026] Figure 13 This indicates a dislocation density of 6.2 × 10⁻⁶. 4 / cm 2 Scanning electron microscope images of the distribution of corrosion pits after surface grinding and etching of the OVPE-GaN layer.

[0027] Figure 14 This indicates a dislocation density of 6.4 × 10⁻⁶.4 / cm 2 Scanning electron microscope images of the distribution of corrosion pits after surface grinding and etching of the OVPE-GaN layer.

[0028] Figure 15 This indicates a dislocation density of 5.7 × 10⁻⁶. 4 / cm 2 Scanning electron microscope images of the distribution of corrosion pits after surface grinding and etching of the OVPE-GaN layer.

[0029] Figure 16 This indicates a dislocation density of 4.3 × 10⁻⁶. 6 / cm 2 Scanning electron microscope images of the distribution of corrosion pits after surface grinding and etching of the HVPE-GaN layer.

[0030] Figure 17 This is a flowchart of the manufacturing method of the group III nitride substrate according to Embodiment 1.

[0031] Figure 18 This is a schematic diagram showing the structure of the manufacturing apparatus for the group III nitride substrate according to Embodiment 1.

[0032] Figure 19 It means Figure 18 A schematic diagram of a modified example of a manufacturing apparatus for a group III nitride substrate.

[0033] Symbol explanation:

[0034] 1. Substrate, 2. Growth layer, 3. Etching pit, 10. Group III nitride substrate, 11. First region, 12. Second region, 13. Third region, 20. Analytical range, 100. Raw material chamber, 101. Raw material reaction chamber, 102. First transport gas supply port, 103. Reactive gas supply pipe, 104. Raw material boat, 105. Starting Ga source (starting Group III element source), 106. First heater, 107. Group III oxide gas outlet, 108. Group III oxide gas and transport gas outlet, 109. Connecting pipe, 110. Third heater, 111. Growth chamber, 112. Nitrogen-containing gas supply port, 113. Oxidized gas supply port, 114. Second transport gas supply port, 115. Second heater, 116. Substrate, 117. Substrate base, 118. Group III oxide gas and transport gas supply port, 119. Exhaust port, 150. Manufacturing apparatus for Group III nitride substrate. Detailed Implementation

[0035] The first type of group III nitride substrate has a first region displaying a first impurity concentration and a second region displaying a second impurity concentration lower than the first impurity concentration in its polished surface.

[0036] The first dislocation density in the first region is lower than the second dislocation density in the second region.

[0037] For the group III nitride substrate of the second method, in the above first method, the first region may be configured to surround the periphery of the second region with the second region as the center.

[0038] For the group III nitride substrate of the third method, in the above first or second method, the first region may have a shape with a reduced diameter towards the second region.

[0039] For the group III nitride substrate of the fourth method, in any one of the above first to third methods, it may further have a third region showing a third impurity concentration lower than the second impurity concentration.

[0040] For the group III nitride substrate of the fifth method, in the above fourth method, the third region may be configured to surround the periphery of the second region with the second region as the center.

[0041] For the group III nitride substrate of the sixth method, in the above fourth method, the first region and the third region may be alternately arranged around the second region with the second region as the center.

[0042] For the group III nitride substrate of the seventh method, in any one of the above first to sixth methods, the impurity contained in the first region is at least one selected from oxygen and silicon.

[0043] For the group III nitride substrate of the eighth method, in any one of the above first to seventh methods, the oxygen concentration of the first impurity concentration is 1×10 20 / cm[[ID=*26]] 3 or more.

[0044] The device of the ninth method includes the group III nitride substrate of any one of the above first to eighth methods, and a device structure formed on the group III nitride substrate.

[0045] Hereinafter, while referring to the drawings, the group III nitride substrate of the embodiment will be described. It should be noted that the same reference numerals are assigned to substantially the same components in the drawings.

[0046] (Embodiment 1)

[0047] <Group III nitride substrate>

[0048] Figure 1 is a cross-sectional view of the group III nitride substrate of Embodiment 1 as viewed from the m-plane. Figure 2This is a cross-sectional view of the group III nitride substrate of Embodiment 1 as seen from side a. Figure 3 This is a scanning electron microscope image showing the distribution of corrosion pits 3 after surface grinding and etching of the group III nitride substrate of Embodiment 1. Figure 4 It means Figure 3 Cathodic emission (CL) image of surface dislocations observed from the c-axis on a group III nitride substrate.

[0049] In Embodiment 1, the group III nitride substrate has, for example, a polished surface, such as... Figure 1 and Figure 2 As shown, a GaN layer 2 is grown on a seed substrate 1. Furthermore, on the surface of the GaN layer 2, as... Figure 1 The cross-sectional view observed from plane m shows planes {11-22}. Furthermore, as... Figure 2 The cross-sectional view observed from plane a shows that it has planes {10-11}. Additionally, as... Figure 3 SEM photos and Figure 4 As shown in the cathodic emission image after surface polishing, six regions 11 on the {11-22} plane and six regions 13 on the {10-11} plane surround the second region 12, which serves as an corrosion pit. Regions 11 and 13 are alternately arranged around the second region 12. Furthermore, regions 11 and 13 taper towards the second region 12. In other words, regions 11 and 13 extend radially around the second region 12. Additionally, regions 11 and 13 are arranged around each of the second regions 12, which serve as corrosion pits.

[0050] It should be noted that, as Figure 3 As shown in the SEM image, it can be seen that the density of etch pits 3 on the surface of the group III nitride substrate in this embodiment 1 is low, that is, the dislocation density is low.

[0051] <Regarding impurity concentration>

[0052] Figure 5 It represents a cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate, with an analytical range of 20 based on secondary ion mass spectrometry. Figure 6 yes Figure 5 The range of microscopic images analyzed. Figure 7 It is aimed at Figure 5 The analytical range will be represented by a graph showing the concentration of oxygen obtained by secondary ion mass spectrometry. Figure 8 It is aimed at Figure 5 The analytical range will be represented by a graph showing the concentration of Si obtained by secondary ion mass spectrometry.

[0053] The group III nitride substrate, for example, is as follows Figure 7 As shown, the oxygen concentration in region 11 is 10. 20 / cm 2 In the latter half of the interval, the oxygen concentration in region 3, area 13, is 10. 20 / cm 2 The first half of the interval. That is, the oxygen concentration in region 11 is higher than the oxygen concentration in region 33. It is also known that the oxygen concentration in region 21 is lower than that in region 11 but higher than that in region 33. Furthermore, the first dislocation density in region 11 is lower than the second dislocation density in region 22. It should be noted that, as... Figure 8 As shown, the Si concentration is 10 in regions 11, 12, and 13. 18 / cm 2 First half ~ 10 19 / cm 2 In the latter half of the interval, there are no major differences between the regions; the difference in impurity concentration depends on the oxygen concentration.

[0054] <Regarding the thickness and dislocation density of the growth layer>

[0055] Figure 9 This represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate with an OVPE-GaN layer thickness of 50 μm. Figure 10 This represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate with an OVPE-GaN layer thickness of 200 μm. Figure 11 This represents the cathodic emission (CL) image of surface dislocations observed from the c-axis of a group III nitride substrate with an OVPE-GaN layer thickness of 300 μm. Figure 12 This is a graph showing the relationship between the thickness of the OVPE-GaN layer and the dislocation density.

[0056] like Figures 9 to 11 As shown, it can be seen that with the effect of Figure 1 and Figure 2 As the thickness of the GaN layer 2 in the growth layer increases, the number of regions 12 decreases. That is, as... Figure 12 As shown, the dislocation density decreases with increasing thickness of the GaN layer 2 grown on the seed substrate 1. Specifically, in the case of HVPE-GaN in the seed substrate 1, the dislocation density is as high as approximately 3 × 10⁻⁶. 6 cm -2 When the thickness of GaN layer 2 is 200 μm, the dislocation density is approximately 1.5 × 10⁻⁶. 5 cm -2 When the thickness of GaN layer 2 is 300 μm, the dislocation density is as low as approximately 8 × 10⁻⁶. 4 cm -2. When considering the dislocation density, the thickness of the GaN layer 2 is preferably 200 μm or more, and more preferably 300 μm or more.

[0057] Figure 13 It shows the scanning electron microscope image of the distribution of etch pits after surface polishing and etching of the surface of an OVPE-GaN layer with a dislocation density of 6.2×10 4 / cm 2 . Figure 14 It shows the scanning electron microscope image of the distribution of etch pits after surface polishing and etching of the surface of an OVPE-GaN layer with a dislocation density of 6.4×10 4 / cm 2 . Figure 15 It shows the scanning electron microscope image of the distribution of etch pits after surface polishing and etching of the surface of an OVPE-GaN layer with a dislocation density of 5.7×10 4 / cm 2 . Figure 16 It shows the scanning electron microscope image of the distribution of etch pits after surface polishing and etching of the surface of a HVPE-GaN layer with a dislocation density of 4.3×10 6 / cm 2 .

[0058] As Figure 16 shown, the surface of the GaN layer of the substrate 1 based on the HVPE method (hydride vapor phase epitaxy method) has a very high dislocation density. On the other hand, by providing a GaN layer 2 grown by the OVPE method (oxide vapor phase epitaxy method) on the above-mentioned substrate 1, as Figures 12 to 15 shown, the dislocation density can be reduced by approximately two orders of magnitude.

[0059] According to this group-III nitride substrate, the dislocation is low and the resistance is low. Therefore, even when a device is formed thereon, by increasing the impurity concentration in the first region with a low dislocation density, current can preferentially flow through the low-resistance first region. As a result, leakage in the second region with a high dislocation density can be suppressed, and an improvement in the breakdown voltage can be achieved.

[0060] <Outline of the manufacturing method of the group-III nitride substrate>

[0061] Refer to Figure 17The flowchart below provides an overview of the method for manufacturing a group III nitride substrate according to Embodiment 1 of the present invention. The method for manufacturing a group III nitride substrate according to Embodiment 1 includes: a reactive gas supply step (S01), a group III element oxide gas generation step (S02), a group III element oxide gas supply step (S03), a nitrogen-containing gas supply step (S04), an oxidizable gas supply step (S05), a group III nitride crystal generation step (S06), an oxidizable gas reaction step (S07), and a residual gas removal step (S08). The method for manufacturing this group III nitride substrate is characterized by the growth of a GaN layer based on the OVPE method using group III element oxide gas as a raw material.

[0062] (1) In the reactive gas supply process, reactive gas (SO1) is supplied to the raw material reaction chamber.

[0063] (2) In the process of generating group III element oxide gas, the initial group III element source is reacted with a reactive gas (a reducing gas when the initial group III element source is an oxide, and an oxidizing gas when it is a metal) to generate group III element oxide gas (SO2).

[0064] (3) In the process of supplying group III element oxide gas, group III element oxide gas (SO3) generated in the process of generating group III element oxide gas is supplied to the growth chamber.

[0065] (4) In the process of supplying nitrogen-containing gas, nitrogen-containing gas (SO4) is supplied to the growth chamber.

[0066] (5) In the process of supplying oxidizing gas, oxidizing gas (S05) is supplied to the growth chamber.

[0067] (6) In the process of generating group III nitride crystals, the group III element oxide gas supplied to the growth chamber in the process of supplying group III element oxide gas reacts with the nitrogen-containing gas supplied to the growth chamber in the process of supplying nitrogen-containing gas to generate group III nitride crystals (SO6).

[0068] (7) In the oxidizing gas reaction process, the oxides other than the group III element oxide gas supplied to the growth chamber react with the oxidizing gas to suppress the mixing of oxygen into the group III nitride crystal (S07).

[0069] (8) In the residual gas discharge process, unreacted gases that do not participate in the formation of group III nitride crystals are discharged to the outside (S08).

[0070] By using the above respective processes, a group-III nitride substrate on which a group-III nitride crystal has grown on a seed substrate can be produced.

[0071] <Outline of the manufacturing apparatus for a group-III nitride substrate>

[0072] Refer to Figure 18 and Figure 19 a schematic diagram showing the structure of a manufacturing apparatus 150 for a group-III nitride substrate, and an outline of the manufacturing apparatus 150 for a group-III nitride substrate according to Embodiment 1 of the present invention will be described.

[0073] It should be noted that Figure 18 and Figure 19 in, the sizes, ratios, etc. of the respective constituent members may be different from the actual ones. In the manufacturing apparatus 150 for a group-III nitride substrate according to Embodiment 1, a raw material reaction chamber 101 is disposed in a raw material chamber 100, and a raw material boat 104 on which a starting group-III element source 105 is placed is disposed in the raw material reaction chamber 101. In the raw material reaction chamber 101, a reactive gas supply pipe 103 for supplying a gas that reacts with the starting group-III element source 105 is connected, and further has a group-III oxide gas discharge port 107. As the reactive gas, a reducing gas is used when the starting group-III source is an oxide, and an oxidizing gas is used when it is a metal. In addition, in the raw material chamber 100, a first transport gas supply port 102 is provided, and the group-III oxide gas and the transport gas flow from the group-III oxide gas and transport gas discharge port 108 to the growth chamber 111 through a connection pipe 109. The growth chamber 111 has a group-III oxide gas and transport gas supply port 118, an oxidizing gas supply port 113, a nitrogen-containing element gas supply port 112, a second transport gas supply port 114, and an exhaust port 119, and has a substrate susceptor 117 on which a seed substrate 116 is provided.

[0074] <Details of the manufacturing method and manufacturing apparatus>

[0075] Using Figure 18 and Figure 19 , details of the manufacturing method of the group-III nitride substrate according to Embodiment 1 will be described.

[0076] Here, the case where metallic Ga is used as the starting group-III element source 105 will be described.

[0077] (1) In the reactive gas supply process, a reactive gas is supplied from the reactive gas supply pipe 103 to the raw material reaction chamber 101.

[0078] (2) In the process of generating Group III element oxide gas, the reactive gas supplied to the raw material reaction chamber 101 in the reactive gas supply process reacts with metallic Ga, which serves as the starting Group III element source 105, to generate Ga2O gas, which is a Group III oxide gas. The generated Ga2O gas is discharged from the raw material reaction chamber 101 to the raw material chamber 100 via the Group III oxide gas outlet 107. The discharged Ga2O gas is mixed with the first transport gas supplied to the raw material chamber from the first transport gas supply port 102 and supplied to the Group III oxide gas and transport gas outlet 108. Here, the temperature of the first heater 106 is set to 800°C or higher from the viewpoint of the boiling point of Ga2O gas, and is set to less than 1800°C to be lower than the temperature of the second heater 115. The starting Ga source is placed in the raw material boat 104. The raw material boat 104 is preferably shaped to increase the contact area between the reactive gas and the starting Ga source.

[0079] It should be noted that the methods for generating Group III oxide gases generally fall into two categories: reducing the starting Ga source 105 and oxidizing the starting Ga source 105. For example, in the reduction method, an oxide (e.g., Ga₂O₃) is used as the starting Ga source 105, and a reducing gas (e.g., H₂, CO, CH₄, C₂H₆, H₂S, SO₂) is used as the reactive gas. On the other hand, in the oxidation method, a non-oxide (e.g., liquid Ga) is used as the starting Ga source 105, and an oxidizing gas (e.g., H₂O, O₂, CO) is used as the reactive gas. For example, Group III oxide gases can be generated using the following formula (I).

[0080] 2Ga + H₂O → Ga₂O + H₂ (I)

[0081] In addition to the starting Ga source 105, In or Al sources can also be used as the starting group III elements. An inert gas or H2 gas can be used as the first transport gas.

[0082] (3) In the Group III element oxide gas supply process, the Ga2O gas generated in the Group III element oxide gas generation process is supplied to the growth chamber 111 via the Group III oxide gas and transport gas outlet 108, the connecting pipe 109, and the Group III oxide gas and transport gas supply port 118. If the temperature of the connecting pipe 109 connecting the raw material chamber 100 and the growth chamber 111 is lower than the temperature of the raw material chamber 100, a reverse reaction will occur, resulting in the precipitation of the initial Ga source 105 within the connecting pipe 109. Therefore, to ensure that the temperature does not fall below that of the raw material chamber 100, the connecting pipe 109 is heated to a temperature higher than that of the first heater 106 using the third heater 110.

[0083] (4) In the nitrogen-containing gas supply process, nitrogen-containing gas is supplied to the growth chamber 111 from the nitrogen-containing gas supply port 112. As the nitrogen-containing gas, NH3 gas, NO gas, NO2 gas, N2O gas, N2H2 gas, N2H4 gas, etc. can be used.

[0084] (5) In the oxidizing gas supply process, an oxidizing gas is supplied to the growth chamber 111 from the oxidizing gas supply port 113. The reason for supplying the oxidizing gas is to reduce oxide gases other than Group III oxide gases (oxidizing gas reaction process). From the viewpoint of reactivity with oxide gases other than Ga source, B gas, Ga gas, In gas, Tl gas, etc., can be used as the oxidizing gas. In addition, CH4 gas, C2H6 gas, C3H8 gas, C4H gas, etc. can also be used as the oxidizing gas. 10 Gases, including C2H4 gas, C3H6 gas, C4H8 gas, C2H2 gas, C3H4 gas, and HCN gas.

[0085] (6) In the group III nitride crystal formation process, the raw material gases supplied to the growth chamber through each supply process are synthesized to produce group III nitride crystals. The growth chamber 111 is heated to the temperature at which group III oxide gas reacts with nitrogen-containing gas using the second heater 115. At this time, in order to avoid the reverse reaction that generates group III oxide gas, the temperature of the growth chamber 111 is heated to a temperature not lower than that of the raw material chamber 100. Therefore, the temperature of the second heater 115 is set to be above 1000°C and below 1800°C. In addition, based on the reason of suppressing the temperature fluctuation of the growth chamber 111 caused by the Ga2O gas generated in the raw material chamber 100 and the first transport gas, the temperatures of the second heater 115 and the third heater 110 are set to be the same.

[0086] By mixing the Group III oxide gas supplied to the growth chamber 111 through the Group III oxide supply process with the nitrogen-containing gas supplied to the growth chamber 111 through the nitrogen-containing gas supply process upstream of the seed substrate 116, Group III nitride crystals can be grown on the seed substrate 116 using the following formula (II).

[0087] Ga₂O + 2NH₃ → 2GaN + H₂O + 2H₂ (II)

[0088] At this time, in order to suppress the decomposition of nitrogen-containing gas due to heat from the growth chamber 111, it is preferable to cover the nitrogen-containing gas supply port 112 and the outer wall of the growth chamber 111 with heat-insulating material.

[0089] Furthermore, the parasitic growth of Group III nitride crystals onto the furnace wall of the growth chamber 111 and the substrate base 117 can be cited as a problem. Therefore, by controlling the concentration of Group III oxide gas and nitrogen-containing gas by utilizing the transport gas supplied to the growth chamber 111 from the second transport gas supply port 114, the parasitic growth of Group III nitride crystals onto the furnace wall of the growth chamber 111 and the substrate base 117 can be suppressed.

[0090] Additionally, as examples of the seed substrate 116, gallium nitride, gallium arsenide, silicon, sapphire, silicon carbide, zinc oxide, gallium oxide, and ScAlMgO4 can be used.

[0091] As the second transport gas, an inactive gas or H2 gas can be used.

[0092] Furthermore, to reduce the oxygen concentration in the Group III nitride crystal, an oxidizing gas is supplied to the growth chamber 111 via an oxidizing gas supply process. The oxide gas other than the Ga source supplied to the growth chamber 111 via the Group III oxide gas generation and supply processes is due to the increased oxygen concentration in the Group III nitride crystal. Therefore, by reacting the oxide gas other than the Ga source with the oxidizing gas before it reaches the seed substrate 116, the incorporation of oxygen into the crystal can be suppressed. For example, when In gas is used as the oxidizing gas and H2O, which is an oxide gas other than the Ga source, is reacted, In gas reacts with H2O gas to generate In2O gas and H2 gas. In2O gas is extremely difficult to introduce into the solid at growth temperatures exceeding 1000°C, as in the Group III nitride crystal manufacturing method of Embodiment 1.

[0093] It should be noted that unreacted Group III oxide gases, nitrogen-containing gases, oxidized gases, and transport gases are discharged from exhaust port 119 (residual gas discharge process).

[0094] In this method for manufacturing a group III nitride substrate, a GaN layer is grown using an oxide gas of group III elements as a raw material based on the OVPE method. This allows for the formation of pits throughout the substrate, including {11-22} planes (first region) and {10-11} planes (third region) that are crystal faces tilted relative to the c-plane of the GaN layer. As a result, as the grown GaN layer thickens, dislocations are cleared, thereby reducing the dislocation density. As described above, the thickness of the GaN layer to be grown is preferably 200 μm or more. On the other hand, since the GaN layer is grown using the OVPE method (oxide vapor phase epitaxy), pits of 10 μm in-plane density can be formed within the GaN layer. 20 / cm 2 The high oxygen concentration in the latter half of the interval.

[0095] (Example 1)

[0096] Figure 19 In this process, the reactive gas and first transport gas supplied from pipeline 1 to the raw material chamber 100 are set at 4 L / min for H2, 1 L / min for N2, and 0.02 L / min for O2. The second transport gas supplied from pipeline 2 to the growth chamber 111 is set at 2.5 L / min for both H2 and N2. Furthermore, the nitrogen-containing gas supplied from pipeline 3 to the growth chamber 111 is set at 0 L / min for H2, 2.5 L / min for N2, 13-14 L / min for N2, and 1-2 L / min for NH3. The second transport gas supplied from pipeline 4 to the growth chamber 111 is set at 12.5 L / min for both H2 and N2.

[0097] In addition, the temperature of the raw material chamber 100 is set to 1130℃, and the temperature of the growth chamber 111 is set to 1200℃. Resistance heating is used. The atmosphere in the growth chamber 111 is set to atmospheric pressure, and the growth time is set to 460 minutes.

[0098] According to the group III nitride substrate of this embodiment 1, a GaN layer 2 grown by OVPE (oxide vapor phase epitaxy) is formed on the seed substrate 1, thereby reducing the dislocation density by approximately two orders of magnitude compared to the seed substrate 1.

[0099] It should be noted that, in this invention, the appropriate combination of any of the aforementioned implementation methods and / or embodiments can achieve the effects of each implementation method and / or embodiment.

[0100] Industrial availability

[0101] The group III nitride substrate of the present invention has low dislocation density and low resistance, which can suppress leakage in the second region with high dislocation density during device formation and improve the insulation withstand voltage.

Claims

1. A group III nitride substrate, Within the ground surface, there is a first region containing oxygen at a first impurity concentration and a second region containing oxygen at a second impurity concentration lower than the first impurity concentration. The first dislocation density in the first region is lower than the second dislocation density in the second region. The first region is configured to surround the second region with the second region as the center.

2. The group III nitride substrate according to claim 1, wherein, The first region has a shape that narrows towards the second region.

3. The group III nitride substrate according to claim 1, further comprising a third region containing oxygen at a third impurity concentration lower than that of the second impurity concentration.

4. The group III nitride substrate according to claim 3, wherein, The third region is configured to surround the second region with the second region as the center.

5. The group III nitride substrate according to claim 3, wherein, The first region and the third region are alternately arranged around the second region along a circumferential direction.

6. The group III nitride substrate according to claim 1, wherein, As an impurity contained in the first region, it also contains silicon.

7. The group III nitride substrate according to claim 1, wherein the oxygen concentration is 1 × 10⁻⁶ for the first impurity concentration. 20 / cm 3 above.

8. A device comprising: The group III nitride substrate according to any one of claims 1 to 7, and Device structure formed on the group III nitride substrate.

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