Group-iii nitride substrate

Abstract

To provide a low-dislocation and low-resistance group-III nitride substrate while achieving a high carrier concentration.SOLUTION: A group-III nitride substrate is a group-III nitride substrate including a GaN layer, the GaN layer comprising a plurality of first regions containing oxygen at a first impurity concentration, a plurality of third regions containing oxygen at a third impurity concentration lower than the first impurity concentration, and a second region containing oxygen at a second impurity concentration higher than the third impurity concentration, wherein the plurality of first regions and the plurality of third regions are alternately arranged circumferentially around the second region, a principal surface of the GaN layer is a c-plane, and the GaN layer is an epitaxial layer.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a group III nitride substrate. [Background technology]

[0002] Conventionally, vertical GaN power devices require GaN substrates with low resistance and low dislocations. For example, when fabricating n-type low-resistivity GaN substrates, the carrier concentration has been improved by increasing the amount of Si atoms or O atoms mixed in (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-132558 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the carrier concentration is 1×10 20 / cm 3 If the concentration is higher than this, problems such as deterioration of crystallinity and an increase in dislocation defects may occur.

[0005] An object of the present invention is to provide a group III nitride substrate that has low dislocations and low resistance while achieving a high carrier concentration. [Means for solving the problem]

[0006] The group III nitride substrate according to the present invention comprises a first region exhibiting a first impurity concentration within a polished surface; a second region exhibiting a second impurity concentration lower than the first impurity concentration; and The first region has a first dislocation density lower than the second dislocation density in the second region. [Effects of the Invention]

[0007] The III-nitride substrate according to the present invention has low dislocations and low resistance, and can suppress leakage current from occurring in the second region with high dislocation density during device formation, thereby improving the dielectric strength. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a group III nitride substrate according to a first embodiment, viewed from the m-plane. [Figure 2] 1 is a cross-sectional view of a III-nitride substrate according to a first embodiment, viewed from its a-plane. [Figure 3] 2 is a scanning electron microscope photograph showing the distribution of etch pits after surface polishing and etching of the surface of the group III nitride substrate according to the first embodiment. [Figure 4] 4 is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of the group III nitride substrate of FIG. 3. [Figure 5] This is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a group III nitride substrate, illustrating the range of analysis by secondary ion mass spectrometry. [Figure 6] This is a microscope image of the analysis area in Figure 5. [Figure 7] FIG. 6 is a diagram showing the oxygen concentration obtained by secondary ion mass spectrometry as shading for the analysis range of FIG. 5. [Figure 8] FIG. 6 is a diagram showing the Si concentration obtained by secondary ion mass spectrometry as a shade of gray for the analysis range of FIG. 5. [Figure 9] This is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a group III nitride substrate when the OVPE-GaN layer is 50 μm thick. [Figure 10] This is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a group III nitride substrate when the OVPE-GaN layer is 200 μm thick. [Figure 11]This is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a group III nitride substrate when the OVPE-GaN layer is 300 μm thick. [Figure 12] FIG. 1 is a graph showing the relationship between the thickness of an OVPE-GaN layer and the dislocation density. [Figure 13] 1 is a scanning electron microscope photograph showing 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] 1 is a scanning electron microscope photograph showing 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] 1 is a scanning electron microscope photograph showing 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] 1 is a scanning electron microscope photograph showing the distribution of etch pits after surface polishing and etching of the surface of an HVPE-GaN layer with a dislocation density of 4.3×10 6 / cm 2 . [Figure 17] 3 is a flowchart of a method for manufacturing a group III nitride substrate according to the first embodiment. [Figure 18] 1 is a schematic diagram showing the configuration of a manufacturing apparatus for a group III nitride substrate according to a first embodiment. [Figure 19] FIG. 19 is a schematic diagram showing a modification of the group III nitride substrate manufacturing apparatus of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] The group III nitride substrate according to the first aspect comprises a first region exhibiting a first impurity concentration within a polished surface; a second region exhibiting a second impurity concentration lower than the first impurity concentration; and The first region has a first dislocation density lower than the second dislocation density in the second region.

[0010] A III-nitride substrate according to a second aspect may be the above-mentioned first aspect, wherein the first region is disposed so as to surround the periphery of the second region with the second region as the center.

[0011] A group III nitride substrate according to a third aspect may be the substrate of the first or second aspect, wherein the first region has a shape that tapers toward the second region.

[0012] A III-nitride substrate according to a fourth aspect may be any one of the first to third aspects, further comprising a third region exhibiting a third impurity concentration lower than the second impurity concentration.

[0013] A III-nitride substrate according to a fifth aspect may be the fourth aspect, wherein the third region is disposed so as to surround the periphery of the second region with the second region as the center.

[0014] A III-nitride substrate according to a sixth aspect is the fourth aspect, wherein the first regions and the third regions may be alternately arranged around the second region with the second region at the center.

[0015] A Group III nitride substrate according to a seventh aspect is any one of the first to sixth aspects, wherein the impurity contained in the first region may be at least one selected from the group consisting of oxygen and silicon.

[0016] A Group III nitride substrate according to an eighth aspect is the substrate according to any one of the first to seventh aspects, wherein the first impurity concentration is an oxygen concentration of 1×10 20 / cm 3 It may be more than that.

[0017] A device according to a ninth aspect comprises a group III nitride substrate according to any one of the first to eighth aspects; a device structure formed on the III-nitride substrate; Equipped with.

[0018] Hereinafter, the group III nitride substrate according to the embodiment will be described while referring to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

[0019] (Embodiment 1) <Group III nitride substrate> FIG. 1 is a cross-sectional view of the group III nitride substrate according to Embodiment 1 as seen from the m-plane. FIG. 2 is a cross-sectional view of the group III nitride substrate according to Embodiment 1 as seen from the a-plane. FIG. 3 is a scanning electron microscope photograph showing the distribution of etch pits 3 after surface polishing and etching of the surface of the group III nitride substrate according to Embodiment 1. FIG. 4 is a cathode luminescence (CL) image showing surface dislocations as seen from the c-axis of the group III nitride substrate of FIG. 3. The group III nitride substrate according to Embodiment 1 has, in the polished plane, for example, a GaN layer 2 grown on a seed substrate 1 as shown in FIGS. 1 and 2. Further, on the surface of the GaN layer 2, as shown in the cross-sectional view seen from the m-plane of FIG. 1, it has a {11-22} plane. Furthermore, as shown in the cross-sectional view seen from the a-plane of FIG. 2, it has a {10-11} plane. Also, as shown in the SEM photograph of FIG. 3 and the cathode luminescence image after surface polishing of FIG. 4, six first regions 11 of the {11-22} plane and six third regions 13 of the {10-11} plane are respectively arranged surrounding the periphery of a second region 12 which is an etch pit. The first region 11 and the third region 13 are alternately arranged around the second region 12. Furthermore, the first region 11 and the third region 13 are reduced in diameter toward the second region 12. In other words, the first region 11 and the third region 13 extend radially around the second region 12. Also, the first region 11 and the third region 13 are arranged around the periphery of each second region 12 which is an etch pit. As shown in the SEM photograph of FIG. 3, it can be seen that the density of the etch pits 3 is low on the surface of the group III nitride substrate according to this Embodiment 1, that is, the dislocation density is low.

[0020] <Regarding impurity concentration> Fig. 5 is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a group III nitride substrate, illustrating an analysis area 20 by secondary ion mass spectrometry. Fig. 6 is a microscope image of the analysis area of Fig. 5. Fig. 7 is a graph showing the oxygen concentration obtained by secondary ion mass spectrometry as a shading for the analysis area of Fig. 5. Fig. 8 is a graph showing the Si concentration obtained by secondary ion mass spectrometry as a shading for the analysis area of Fig. 5. In this III-nitride substrate, for example, as shown in FIG. 7, the oxygen concentration in the first region 11 is 10 20 / cm 2 The oxygen concentration in the third region 13 is 10 20 / cm 2 8, the oxygen concentration in the first region 11 is higher than that in the third region 13. In addition, it can be seen that the oxygen concentration in the second region 12 is lower than that in the first region 11 and higher than that in the third region 13. In addition, the first dislocation density in the first region 11 is lower than the second dislocation density in the second region 12. As shown in FIG. 8, the Si concentration is 10 throughout the first region 11, the second region 12, and the third region 13. 18 / cm 2 First half - 10 19 / cm 2 In the latter half of the 1000s, there is no significant difference between the regions, and the difference in impurity concentration depends on the oxygen concentration.

[0021] <Growth layer thickness and dislocation density> Figure 9 is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a III-nitride substrate when the OVPE-GaN layer is 50 μm thick. Figure 10 is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a III-nitride substrate when the OVPE-GaN layer is 200 μm thick. Figure 11 is a cathodoluminescence (CL) image showing surface dislocations as viewed from the c-axis of a III-nitride substrate when the OVPE-GaN layer is 300 μm thick. Figure 12 is a graph showing the relationship between OVPE-GaN layer thickness and dislocation density. 9 to 11, it can be seen that the number of second regions 12 decreases as the thickness of GaN layer 2, which is the growth layer in FIGS. 1 and 2, increases. In other words, as shown in FIG. 12, it can be seen that the dislocation density decreases as the thickness of GaN layer 2 grown on seed substrate 1 increases. Specifically, in the case of HVPE-GaN on seed substrate 1, the dislocation density was about 3×10 6 cm -2 The dislocation density is high at 200 μm thickness of GaN layer 2, whereas the dislocation density is about 1.5 × 10 5 cm -2 , the thickness of the GaN layer 2 is 300 μm and the dislocation density is about 8 × 10 4 cm -2 Considering the dislocation density, it is preferable that the thickness of the GaN layer 2 is approximately 200 μm or more. Furthermore, it is more preferable that the thickness of the GaN layer 2 is 300 μm or more.

[0022] Figure 13 shows the dislocation density of 6.2 × 10 4 / cm 2 Figure 14 shows a scanning electron microscope image of the OVPE-GaN layer after surface polishing and etching, showing the distribution of etch pits. 4 / cm 2 Figure 15 shows a scanning electron microscope image of the OVPE-GaN layer after surface polishing and etching, showing the distribution of etch pits. 4 / cm 2 Figure 16 is a scanning electron microscope photograph showing the distribution of etch pits after surface polishing and etching of the OVPE-GaN layer. 6 / cm 2 1 is a scanning electron microscope photograph showing the distribution of etch pits on the surface of the HVPE-GaN layer after surface polishing and etching. As shown in Fig. 16, the surface of the GaN layer grown by HVPE (hydride vapor phase epitaxy) on the seed substrate 1 has an extremely high dislocation density. On the other hand, by providing a GaN layer 2 grown by OVPE (oxide vapor phase epitaxy) on the seed substrate 1, the dislocation density can be reduced by about two orders of magnitude, as shown in Figs. 12 to 15. According to this group-III nitride substrate, it has a low dislocation density and a low resistance. Therefore, even when a device is formed thereon, by increasing the impurity concentration in the first region with a low dislocation density, electricity can be preferentially passed through the first region with a reduced resistance. As a result, leakage in the second region with a high dislocation density can be suppressed, and the breakdown voltage can be improved.

[0023] <Overview of the manufacturing method of the group-III nitride substrate> The overview of the manufacturing method of the group-III nitride substrate according to Embodiment 1 of the present disclosure will be described with reference to the flowchart of FIG. 17. The manufacturing method of the 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 element-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 discharge step (S08). This manufacturing method of the group-III nitride substrate is characterized by growing a GaN layer by an OVPE method using a group-III element oxide gas as a raw material. (1) In the reactive gas supply step, a reactive gas is supplied to the raw material reaction chamber (S01). (2) In the group-III element oxide gas generation step, a starting group-III element source and a reactive gas (a reducing gas when the starting group-III element source is an oxide, and an oxidizing gas when it is a metal) are reacted to generate a group-III element oxide gas (S02). (3) In the group-III element oxide gas supply step, the group-III element oxide gas produced in the group-III element oxide gas generation step is supplied to the growth chamber (S03). (4) In the nitrogen element-containing gas supply step, a nitrogen element-containing gas is supplied to the growth chamber (S04). (5) In the oxidizable gas supply step, an oxidizable gas is supplied to the growth chamber (S05). (6) In the process of growing group III nitride crystals, the group III element oxide gas supplied into the growth chamber in the group III element oxide gas supply process and the nitrogen element-containing gas supplied into the growth chamber in the nitrogen element-containing gas supply process are reacted to generate group III nitride crystals (S06). (7) In the oxidizable gas reaction process, an oxide other than the group III element oxide gas supplied into the growth chamber is reacted with the oxidizable gas to suppress the incorporation of oxygen into the group III nitride crystals (S07). (8) In the residual gas discharge process, unreacted gas that does not contribute to the generation of group III nitride crystals is discharged outside the chamber (S08). Through the above respective processes, a group III nitride substrate on which group III nitride crystals are grown on a seed substrate can be produced.

[0024] <Overview of the manufacturing apparatus for group III nitride substrates> The overview of the manufacturing apparatus 150 for group III nitride substrates according to Embodiment 1 of the present disclosure will be described with reference to the schematic diagrams showing the configuration of the manufacturing apparatus 150 for group III nitride substrates in FIGS. 18 and 19. In FIGS. 18 and 19, the sizes, ratios, etc. of each component member may be different from the actual ones. The manufacturing apparatus 150 for group III nitride substrates according to Embodiment 1 has a raw material reaction chamber 101 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. A reactive gas supply pipe 103 for supplying a gas that reacts with the starting group III element source 105 is connected to the raw material reaction chamber 101, and it has a group III oxide gas discharge port 107. The reactive gas uses a reducing gas when the starting group III source is an oxide, and an oxidizing gas when it is a metal. Further, the raw material chamber 100 is provided with a first carrier gas supply port 102, and the group III oxide gas and the carrier gas flow from the group III oxide gas and carrier gas discharge port 108 through a connecting pipe 109 to the growth chamber 111. The growth chamber 111 has a group III oxide gas and carrier gas supply port 118, an oxidizable gas supply port 113, a nitrogen element-containing gas supply port 112, a second carrier gas supply port 114, and an exhaust port 119, and includes a substrate susceptor 117 on which a seed substrate 116 is placed.

[0025] <Details of manufacturing method and manufacturing equipment> The method for manufacturing a group III nitride substrate according to the first embodiment will be described in detail with reference to FIGS. Here, a case where metallic Ga is used as the starting group III element source 105 will be described. (1) In the reactive gas supply step, a reactive gas is supplied to the raw material reaction chamber 101 through the reactive gas supply pipe 103 . (2) In the Group III element oxide gas generation process, the reactive gas supplied to the raw material reaction chamber 101 in the reactive gas supply process reacts with metallic Ga, which is the starting Group III element source 105, to generate GaO gas, which is a Group III oxide gas. The generated GaO 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 GaO gas is mixed with the first carrier gas supplied to the raw material chamber from the first carrier gas supply port 102, and supplied to the Group III oxide gas and carrier gas outlet 108. Here, the temperature of the first heater 106 is set to 800°C or higher in consideration of the boiling point of GaO gas, and to less than 1800°C so as to be lower than that 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.

[0026] Methods for generating Group III oxide gases can be broadly divided into methods for reducing the starting Ga source 105 and methods for 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 gas, CO gas, CH4 gas, C2H6 gas, HS gas, SO2 gas) 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., HO gas, O2 gas, CO gas) is used as the reactive gas. For example, Group III oxide gas can be generated by the following formula (I): 2Ga+H2O → Ga2O+H2(I) In addition to the starting Ga source 105, an In source or an Al source can be used as the starting Group III element. Here, an inert gas or H2 gas can be used as the first carrier gas.

[0027] (3) In the Group III element oxide gas supply step, the GaO gas generated in the Group III element oxide gas generation step is supplied to the growth chamber 111 via the Group III oxide gas and carrier gas outlet 108, the connecting pipe 109, and the Group III oxide gas and carrier gas inlet 118. When the temperature of the connecting pipe 109 connecting the source chamber 100 and the growth chamber 111 drops below the temperature of the source chamber 100, a reverse reaction of the reaction for generating the Group III oxide gas occurs, and the starting Ga source 105 precipitates in the connecting pipe 109. Therefore, the connecting pipe 109 is heated by the third heater 110 to a temperature higher than that of the first heater 106 so as not to drop below the temperature of the source chamber 100.

[0028] (4) In the nitrogen-containing gas supply step, a nitrogen-containing gas is supplied to the growth chamber 111 from the nitrogen-containing gas supply port 112. Examples of the nitrogen-containing gas that can be used include NH3 gas, NO gas, NO2 gas, N2O gas, N2H2 gas, and N2H4 gas.

[0029] (5) In the oxidizable gas supply step, an oxidizable gas is supplied to the growth chamber 111 from the oxidizable gas supply port 113. The reason for supplying the oxidizable gas is to reduce oxide gases other than Group III oxide gases (oxidizable gas reaction step). As the oxidizable gas, B gas, Ga gas, In gas, Tl gas, etc. can be used from the viewpoint of reactivity with oxide gases other than Ga source. Furthermore, as the oxidizable gas, CH4 gas, C2H6 gas, C3H8 gas, CH4H 10 It is also possible to use gases such as C2H4 gas, C3H6 gas, C4H8 gas, C2H2 gas, C3H4 gas, and HCN gas.

[0030] (6) In the Group III nitride crystal growth process, the source gases supplied into the growth chamber through each supply process are synthesized to produce Group III nitride crystals. The growth chamber 111 is heated by the second heater 115 to a temperature at which the Group III oxide gas and the nitrogen-containing gas react. At this time, the temperature of the growth chamber 111 is heated so as not to drop below the temperature of the source chamber 100, in order to prevent a reverse reaction of the reaction that produces the Group III oxide gas. Therefore, the temperature of the second heater 115 is set to 1000°C or higher and 1800°C or lower. Furthermore, the temperatures of the second heater 115 and the third heater 110 are set to the same temperature to suppress temperature fluctuations in the growth chamber 111 due to the GaO gas generated in the source chamber 100 and the first carrier gas.

[0031] By mixing the group III oxide gas supplied to the growth chamber 111 via the group III oxide supply step and the nitrogen element-containing gas supplied to the growth chamber 111 via the nitrogen element-containing gas supply step upstream of the seed substrate 116, a group III nitride crystal can be grown on the seed substrate 116 according to the following formula (II): Ga2O+2NH3→2GaN+H2O+2H2(II)

[0032] At this time, in order to prevent the nitrogen-containing gas from being decomposed by the 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 a heat insulating material.

[0033] Another problem is the parasitic growth of Group III nitride crystals on the furnace walls of the growth chamber 111 and on the substrate susceptor 117. Therefore, by controlling the concentrations of the Group III oxide gas and the nitrogen-containing gas using the carrier gas supplied to the growth chamber 111 from the second carrier gas supply port 114, it is possible to suppress the parasitic growth of Group III nitride crystals on the furnace walls of the growth chamber 111 and on the substrate susceptor 117.

[0034] The seed substrate 116 may be made of, for example, gallium nitride, gallium arsenide, silicon, sapphire, silicon carbide, zinc oxide, gallium oxide, or ScAlMgO4. The second carrier gas may be an inert gas or H2 gas.

[0035] Furthermore, to reduce the oxygen concentration in the Group III nitride crystal, an oxidizable gas is supplied into the growth chamber 111 via an oxidizable gas supply step. The increase in the oxygen concentration in the Group III nitride crystal is caused by oxide gases other than the Ga source gas supplied to the growth chamber 111 via the Group III oxide gas generation step and the Group III oxide gas supply step. Therefore, by reacting the oxide gases other than the Ga source gas with the oxidizable gas before they reach the seed substrate 116, it is possible to suppress the incorporation of oxygen into the crystal. For example, when In gas is used as the oxidizable gas and H2O, an oxide gas other than the Ga source gas, is reacted with the In gas, the H2O gas reacts to produce In2O gas and H2 gas. In2O gas is extremely difficult to incorporate into the solid at growth temperatures exceeding 1000°C, as in the method for producing a Group III nitride crystal according to the first embodiment. The unreacted group III oxide gas, nitrogen element-containing gas, oxidizable gas, and carrier gas are exhausted from the exhaust port 119 (residual gas exhaust step).

[0036] In this method for manufacturing a group III nitride substrate, the GaN layer is grown by OVPE using a group III element oxide gas as a raw material. This allows for a growth mode in which pits consisting of the {11-22} plane (first region) and the {10-11} plane (third region), which are facets oblique to the c-plane of the GaN layer, are formed over the entire surface of the substrate. As a result, as the grown GaN layer becomes thicker, dislocations are swept up, reducing the dislocation density. As mentioned above, the thickness of the grown GaN layer is preferably 200 μm or more. On the other hand, since the GaN layer is grown by OVPE (oxide vapor phase epitaxy), it is possible to form pits in the plane of the GaN layer, with a pit size of 10 μm or more. 20 / cm 2 It is possible to achieve a high oxygen concentration in the upper half of the range.

[0037] Example 1 In FIG. 19, H is supplied as a reactive gas and a first carrier gas from a line 1 to a source chamber 100. 2 Gas: 4 L / min, N 2 The flow rates of H2 gas and O2 gas were 1 L / min and 0.02 L / min, respectively. As a second carrier gas supplied to the growth chamber 111 from line 2, H2 gas was 2.5 L / min and N2 gas was 2.5 L / min. Furthermore, as a nitrogen-containing gas supplied to the growth chamber 111 from line 3, H2 gas was 0 L / min, N2 gas was 2.5 L / min, N2 gas was 13 to 14 L / min, and NH3 gas was 1 to 2 L / min. As a second carrier gas supplied to the growth chamber 111 from line 4, H2 gas was 12.5 L / min and N2 gas was 12.5 L / min. The temperature of the source chamber 100 was 1130° C., and the temperature of the growth chamber 111 was 1200° C. The heating method was resistance heating. The atmosphere in the growth chamber 111 was atmospheric pressure, and the growth time was 460 minutes.

[0038] In the group III nitride substrate according to Example 1, by providing a GaN layer 2 grown on a seed substrate 1 by OVPE (oxide vapor phase epitaxy), the dislocation density can be reduced by approximately two orders of magnitude compared to the seed substrate 1.

[0039] In addition, the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example. [Industrial Applicability]

[0040] The III-nitride substrate according to the present invention has low dislocations and low resistance, and can suppress leakage current from occurring in the second region with high dislocation density during device formation, thereby improving the dielectric strength. [Explanation of symbols]

[0041] Type 1 board 2 growth layer 3 Etch Pit 10 Group III nitride substrates 11 First area 12 Second area 13 Third area 20 Analysis Scope 100 raw material chamber 101 Raw material reaction chamber 102 First carrier 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 carrier gas outlet 109 Connecting Pipe 110 Third heater 111 Growth Chamber 112 Nitrogen-containing gas supply port 113 Oxidizable gas supply port 114 Second carrier gas supply port 115 Second heater 116 species substrate 117 Substrate susceptor 118 Group III oxide gas and carrier gas supply port 119 Exhaust vent 150 III-nitride substrate manufacturing equipment

Claims

1. A group III nitride substrate having a GaN layer, The GaN layer is a plurality of first regions containing oxygen at a first impurity concentration; a plurality of third regions containing oxygen at a third impurity concentration lower than the first impurity concentration; a second region containing oxygen at a second impurity concentration higher than the third impurity concentration; and the plurality of first regions and the plurality of third regions are alternately arranged in a circumferential direction around the second region, a primary surface of the GaN layer is a c-plane; A Group III nitride substrate, wherein the GaN layer is an epitaxial layer.

2. The number density of the second region is 3×10 6 / cm ２ 2. The III-nitride substrate of claim 1, wherein:

3. The number density of the second region is 1.5×10 ５ / cm ２ 2. The Group III nitride substrate of claim 1, wherein:

4. The III-nitride substrate according to claim 1 , wherein the first region has a shape that tapers toward the second region.

5. The III-nitride substrate according to claim 1 , wherein the third region has a shape that tapers toward the second region.

6. The Group III nitride substrate according to claim 1 , further comprising silicon as an impurity element contained in said first region.

7. The first impurity concentration is an oxygen concentration of 1×10 20 / cm 3 The group III nitride substrate according to claim 1 , wherein:

8. further comprising a GaN substrate on which the GaN layer is epitaxially grown; The III-nitride substrate according to claim 1 , wherein the GaN layer has a dislocation density lower than that of the GaN substrate.

9. A group III nitride substrate according to any one of claims 1 to 8; a device structure formed on the Group III nitride substrate; A device comprising:

10. A group III nitride substrate having a GaN layer, The GaN layer is a plurality of first regions containing oxygen at a first impurity concentration; a plurality of third regions containing oxygen at a third impurity concentration lower than the first impurity concentration; a second region containing oxygen at a second impurity concentration higher than the third impurity concentration; and the first region and the third region have a shape that decreases in diameter toward the second region, a primary surface of the GaN layer is a c-plane; A Group III nitride substrate, wherein the GaN layer is an epitaxial layer.

11. The III-nitride substrate according to claim 10 , wherein the plurality of first regions and the plurality of third regions are alternately arranged in a circumferential direction around the second region.

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