Group III nitride semiconductor epitaxial wafer and device

Abstract

Provided is a group III nitride semiconductor epitaxial wafer in which a group III nitride semiconductor film having a very flat surface is formed on a group III nitride semiconductor to which a high concentration of impurities has been added. The group III nitride semiconductor epitaxial wafer is provided with a group III nitride semiconductor substrate having n-type conductivity and a carrier concentration of 1020 cm-3 or more, and a group III nitride semiconductor film including an epitaxial layer epitaxially grown on the group III nitride semiconductor substrate, and the group III nitride semiconductor film has a thickness of 1 [mu] m to 30 [mu] m (inclusive). In the group III nitride semiconductor substrate, the off-angle formed between the c-axis of the group III nitride semiconductor substrate and the normal line of the surface of the group III nitride semiconductor substrate on which the group III nitride semiconductor film is formed is 0.38-0.6 degree.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a Group III nitride semiconductor epitaxial wafer having a Group III nitride semiconductor substrate and a Group III nitride semiconductor film epitaxially grown thereon, and a device using the Group III nitride semiconductor epitaxial wafer. BACKGROUND

[0002] Group III nitride semiconductors are used in the fields of optical devices such as semiconductor lasers and light emitting diodes, and high-frequency or high-output electronic devices. These semiconductors can be expected to reduce switching loss at power conversion compared to silicon-based devices, and thus have been particularly focused on in recent years. In order to produce high-frequency or high-output electronic devices, it is necessary to produce devices on a high-quality Group III nitride substrate that can suppress the generation of crystal defects in a device layer.

[0003] Methods of manufacturing Group III nitride crystals include, for example, a hydride vapor phase epitaxy method (hereinafter also referred to as an HVPE method), an ammonia thermal method, a sodium flux method, and an oxide vapor phase epitaxy method (hereinafter also referred to as an OVPE method).

[0004] In the HVPE method, which is the most widely used method for producing substrates, a hydrogen halide gas is introduced into a Group III raw material in the form of an element to produce a halide gas, and the produced Group III element halide gas is used as a raw material gas for crystal growth. For example, in the case of growing a gallium nitride crystal, a Ga metal is introduced with an HCl gas to produce gallium chloride (e.g., GaCl2) gas, and the gallium chloride-containing gas is used as a Group III source, thereby implementing high-speed growth of 1 mm / h or more. It is known that in the HVPE method, a Group III nitride crystal having N-type conductivity is obtained mainly by adding a silicon element to the Group III nitride crystal.

[0005] In the OVPE method, an oxide raw material gas is used to add an oxygen element to a Group III nitride crystal at a high concentration to produce a crystal (see, for example, Patent Literature 1). In this method, a Group III oxide gas is reacted with a gas containing a nitrogen element to produce a Group III nitride crystal. In a substrate obtained by this method, the dislocation density is 10 4 cm -2 The OVPE method is one of the means for obtaining a high-quality Group III nitride crystal because the dislocation density is low, around 10

[0006] The III-nitride substrate can be obtained by processing the III-nitride crystal produced by the above method. By forming an epitaxial film of a III-nitride semiconductor on the substrate, a device can be produced. It is known that in the produced epitaxial film, dislocations are inherited from the crystal defects of the substrate to the epitaxial film. On the other hand, dislocations are considered to be a cause of leakage during operation of the device, and therefore, development has been made to not inherit the dislocations of the substrate (for example, refer to Patent Literature 2).

[0007] Prior Art Documents Patent Literature Patent Literature 1: WO2015 / 053341A1 Patent Literature 2: Japanese Patent Application Publication No. 2010-103353 Non-Patent Literature Non-Patent Literature 1: I. C. Kizilyalli et al., Microelectron Reliab. 55, 1654 (2015). SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION However, in recent years, in the HVPE method, the OVPE method, the sodium flux method, and the like, which are the above-described methods of producing a III-nitride crystal, research has been made to reduce the dislocation density of the substrate itself. At present, in most cases, by growing a crystal having a thickness, a substrate having a dislocation density of about 1 x 1010cm 6 -2 or less can be obtained. In the crystal growth of a thin film at the time of device formation, although the dislocation density can be slightly reduced, it is difficult to be greatly reduced compared to the substrate. Therefore, it is not necessary to adopt the method described in Patent Literature 2.

[0009] Further, in recent years, in particular, as a cause of leakage in a vertical power device, research has been made on the fact that the surface of each layer of the device fluctuates in the thickness direction at the time of formation (for example, refer to Non-Patent Literature 1). This is considered to be due to the fluctuation of each layer of the device, or the fluctuation of the electrode formation surface, thereby causing a local electric field concentration, and the like, thereby causing leakage. Therefore, it is suggested that there is a possibility that crystal growth of an epitaxial film having a flat surface is necessary in order to reduce leakage in a device.

[0010] However, in a vertical power device, it is generally configured so that current flows through the substrate portion as well. Therefore, in order to reduce the resistance at the time of operation of the device, it is also necessary to reduce the resistance of the substrate portion. In the above-described method of producing a III-nitride crystal, in the OVPE method, oxygen atoms that function as a donor in a crystal can be easily doped at a high concentration, and a method of producing a low-resistance substrate is also known.

[0011] ​The inventors have developed a method for obtaining a gallium nitride crystal to which oxygen atoms are added at a high concentration, with an oxygen concentration of 4.4 x 10 20 atoms·cm -3 or more than 4.4 x 10 20 atoms·cm -3 The molecular density in a Group III nitride crystal, such as a gallium nitride crystal, is 4.4 x 10 22 cm -3 In gallium nitride, oxygen atoms are incorporated into the crystal in place of nitrogen atoms, and can be said to be added at a compositional level at an oxygen concentration of 4.4 x 10 20 atoms·cm -3 atoms·cm

[0012] In a semiconductor crystal, impurities are added to the crystal in order to control electrical properties, but are generally added at a concentration of at most 10 19 atoms·cm -3 atoms·cm

[0013] In addition, in a Group III nitride crystal, there are almost no examples of a crystal to which an impurity has been added at a compositional level being used as a substrate to form an epitaxial film. Furthermore, in a crystal to which an impurity has been added at a compositional level, the lattice constant and other basic physical properties of the crystal deviate from the original values. On the other hand, in an epitaxial film, an impurity is not added at a compositional level, and has physical properties that are relatively close to the original material.

[0014] For example, in a case where the lattice constant of the substrate of the epitaxial film and the base deviates greatly, dislocations based on lattice relaxation are introduced in the epitaxial film, and in addition, warping of the shape occurs in the substrate at the time of formation of the epitaxial film. As a result, deterioration of the surface state of the epitaxial film occurs. That is, when an epitaxial film having a low impurity concentration is formed on a substrate having a very high impurity concentration, it is generally difficult to maintain the crystal quality.

[0015] An object of the present disclosure is to provide a Group III nitride semiconductor epitaxial wafer in which a Group III nitride semiconductor film having a very flat surface is formed on a Group III nitride semiconductor to which a high concentration of impurities has been added.

[0016] Means for solving the problem The Group III nitride semiconductor epitaxial wafer of the present disclosure includes a Group III nitride semiconductor substrate that exhibits n-type conductivity and has a carrier concentration of 10 20 cm -3The above; and the Group III nitride semiconductor film includes an epitaxial layer epitaxially grown on the Group III nitride semiconductor substrate, the thickness of the Group III nitride semiconductor film is 1 μm or more and 30 μm or less, and in the Group III nitride semiconductor substrate, the off angle between the normal line of the surface of the Group III nitride semiconductor substrate on which the Group III nitride semiconductor film is formed and the c-axis of the Group III nitride semiconductor substrate is 0.38 degrees or more and 0.6 degrees or less.

[0017] Effects of Invention The Group III nitride semiconductor epitaxial wafer according to the present disclosure can form a device with reduced leakage and low operating loss. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic cross-sectional view that schematically represents one example of the nitride semiconductor epitaxial wafer of Embodiment 1.

[0019] Figure 2 is a differential interference microscope image of the surface of a gallium nitride film obtained from a Group III nitride semiconductor substrate having different off angles in the example.

[0020] Figure 3 is an atomic force microscope image (AFM image) of a view angle of 90 μm in the example.

[0021] Figure 4 is a differential interference microscope image of the surface of a gallium nitride film obtained from a Group III nitride semiconductor substrate having different off angles in the comparative example.

[0022] Figure 5 is an atomic force microscope image (AFM image) of a view angle of 90 μm in the comparative example.

[0023] Figure 6 is a graph representing the relationship between the surface roughness and the off angle of the substrate in the example and the comparative example. DETAILED DESCRIPTION

[0024] The Group III nitride semiconductor epitaxial wafer according to the first aspect includes a Group III nitride semiconductor substrate, a Group III nitride semiconductor film, and a Group III nitride semiconductor substrate on which the Group III nitride semiconductor film is formed. 20 cm -3 The above; and the Group III nitride semiconductor film includes an epitaxial layer epitaxially grown on the Group III nitride semiconductor substrate, the thickness of the Group III nitride semiconductor film is 1 μm or more and 30 μm or less, and in the Group III nitride semiconductor substrate, the off angle between the normal line of the surface of the Group III nitride semiconductor substrate on which the Group III nitride semiconductor film is formed and the c-axis of the Group III nitride semiconductor substrate is 0.38 degrees or more and 0.6 degrees or less.

[0025] The second method relates to a Group III nitride semiconductor epitaxial wafer in which, in the first method described above, the value of the root mean square roughness RMs of the surface of the Group III nitride semiconductor film in a 50 μm square can be 10 nm or less.

[0026] The third method relates to a Group III nitride semiconductor epitaxial wafer in which, in the second method described above, the value of the root mean square roughness RMs of the surface of the Group III nitride semiconductor film in a 50 μm square can be 5 nm or less, and the offset angle formed by the normal to the surface of the Group III nitride semiconductor substrate and the c-axis of the Group III nitride semiconductor substrate is 0.4 degrees or more and 0.55 degrees or less.

[0027] The fourth method relates to a Group III nitride semiconductor epitaxial wafer in which, in any one of the first to third methods described above, the n-type dopant element of the Group III nitride semiconductor substrate can be oxygen.

[0028] The fifth method relates to a Group III nitride semiconductor epitaxial wafer in which, in any one of the first to fourth methods described above, the main Group III element of the Group III nitride semiconductor substrate can be gallium.

[0029] The sixth method relates to a Group III nitride semiconductor epitaxial wafer in which, in the fifth method described above, the oxygen concentration in the Group III nitride semiconductor substrate is 4.4 x 1018 atoms cm 20 atoms cm -3 or less.

[0030] The seventh method relates to a Group III nitride semiconductor epitaxial wafer in which, in any one of the first to sixth methods described above, the Group III nitride semiconductor film can include an epitaxial layer having a lower carrier concentration than the Group III nitride semiconductor substrate.

[0031] The eighth method relates to a Group III nitride semiconductor epitaxial wafer in which, in any one of the first to seventh methods described above, the Group III nitride semiconductor film can include an epitaxial layer having a carrier concentration of 5 x 1018 atoms cm 16 cm -3 or less.

[0032] The ninth method relates to a Group III nitride semiconductor epitaxial wafer in which, in any one of the first to eighth methods described above, the thickness of the Group III nitride semiconductor film can be 1 μm or more and 8 μm or less.

[0033] The tenth method relates to a device that uses a Group III nitride semiconductor epitaxial wafer according to any one of the first to ninth methods described above.

[0034] The eleventh method for manufacturing a Group III nitride semiconductor epitaxial wafer includes: forming a Group III nitride semiconductor substrate having a surface on which a Group III nitride semiconductor film is epitaxially grown, the Group III nitride semiconductor substrate having a conduction property showing n-type and a carrier concentration of 10 20 cm -3 The above process for manufacturing a Group III nitride semiconductor substrate; a process of polishing a surface of the obtained Group III nitride semiconductor substrate to obtain a Group III nitride semiconductor substrate having a surface on which a Group III nitride semiconductor film is epitaxially grown, the surface having an off-angle of 0.38 degrees or more and 0.6 degrees or less between a normal line and a c-axis of the Group III nitride semiconductor substrate; and a process of epitaxially growing a Group III nitride semiconductor film on the surface of the Group III nitride semiconductor substrate having the off-angle of 0.38 degrees or more and 0.6 degrees or less.

[0035] The twelfth method for manufacturing a Group III nitride semiconductor epitaxial wafer is the above eleventh method, in the process of polishing the Group III nitride semiconductor substrate, the Group III nitride semiconductor substrate is placed so that a normal line of a polishing surface, which is a virtual surface, and a c-axis of the Group III nitride semiconductor substrate have an inclination of 0.38 degrees or more and 0.6 degrees or less, and the surface of the Group III nitride semiconductor substrate is polished to be parallel to the polishing surface, and thus a Group III nitride semiconductor substrate having a surface on which a Group III nitride semiconductor film is epitaxially grown, the surface having an off-angle of 0.38 degrees or more and 0.6 degrees or less between a normal line and a c-axis of the Group III nitride semiconductor substrate can be obtained.

[0036] Hereinafter, a Group III nitride semiconductor epitaxial wafer and a device according to an embodiment of the present disclosure will be described by way of example. However, the present disclosure is not limited by any of the numerical values used in the following description or by the use of specific elements.

[0037] (Embodiment 1) <III nitride semiconductor epitaxial wafer> Figure 1 is a schematic cross-sectional view schematically showing an example of a Group III nitride semiconductor epitaxial wafer according to Embodiment 1.

[0038] The Group III nitride semiconductor epitaxial wafer according to the present disclosure includes at least two layers, i.e., a Group III nitride semiconductor substrate and a Group III nitride semiconductor film including an epitaxial layer epitaxially grown thereon.

[0039] Hereinafter, each component constituting the Group III nitride semiconductor epitaxial wafer will be described.

[0040] <III nitride semiconductor substrate> In order to reduce the on-resistance during operation, the Group III nitride semiconductor substrate preferably has a conduction property showing n-type due to an impurity serving as an n-type dopant, and a carrier concentration of 10 20 cm -3 or more and 1.0 x 1019cm-3or less.

[0041] As shown in Figure 1 Fig. 1, the normal line of the surface of the Group III nitride semiconductor substrate is preferably inclined from the c-axis of the Group III nitride semiconductor crystal having a hexagonal wurtzite crystal structure by 0.38 degrees or more and 0.6 degrees or less, and further preferably by 0.4 degrees or more and 0.55 degrees or less. Hereinafter, this inclination angle is sometimes simply referred to as "deviation angle". Thereby, when forming a Group III nitride semiconductor film including an epitaxial layer on the Group III nitride semiconductor substrate, it is easy to maintain the flatness of the surface.

[0042] The n-type doping element of the Group III nitride semiconductor substrate preferably contains at least one selected from the group consisting of a silicon element, a germanium element, and an oxygen element.

[0043] The n-type doping element of the Group III nitride semiconductor substrate more preferably contains an oxygen element. In this case, in particular, when a Group III nitride semiconductor crystal for a substrate is produced by an OVPE method, it is easy to add an oxygen element to the Group III nitride semiconductor crystal.

[0044] When the oxygen element is a main element as the n-type doping element of the Group III nitride semiconductor substrate, it is preferable to be 4.4 x 10 20 atoms cm -3 The above composition level adds an oxygen element. Thereby, it is easy to make the carrier concentration of the Group III nitride semiconductor substrate 10 20 cm -3 or more.

[0045] <III nitride semiconductor film> The Group III nitride semiconductor film contains an epitaxial layer epitaxially grown on a Group III nitride semiconductor substrate. Its electrical characteristics are determined by the performance required by a device, and regarding the carrier concentration, the polarity, it is not limited to a specific property such as p-type or n-type. However, regarding the flatness of the surface, in order to reduce the leakage current at the time of forming a device, the root mean square roughness (RMS) when measured in a 50 μm square region randomly selected from the surface is preferably 10 nm or less, and further preferably 5 nm or less.

[0046] The epitaxial layer constituting the Group III nitride semiconductor film can be one layer, or a structure of two or more layers.

[0047] The Group III nitride semiconductor film preferably contains at least one epitaxial layer having a carrier concentration of 5 x 10 16 cm -3 or more. By combining a Group III nitride semiconductor film containing an epitaxial layer having a low carrier concentration with a substrate having a high carrier concentration, a device having a low resistance and a high withstand voltage, which has not been realized in the past, is easily realized.

[0048] The thickness of the Group III nitride semiconductor film is preferably 1 μm or more. If the Group III nitride semiconductor film is thinner than 1 μm, a stable surface cannot be sufficiently formed when an epitaxial layer is formed on a substrate, and the surface is likely to become rough depending on the flatness of the substrate.

[0049] The thickness of the Group III nitride semiconductor film is preferably 1 μm or more. If the Group III nitride semiconductor film is thinner than 1 μm, a stable surface cannot be sufficiently formed when an epitaxial layer is formed on a substrate, and the surface is likely to become rough depending on the flatness of the substrate.

[0050] The thickness of the Group III nitride semiconductor film is preferably 30 μm or less. If the thickness exceeds 30 μm, the flatness of the surface is sometimes difficult to maintain due to the influence of lattice mismatch. If the thickness is 30 μm or less, the flatness of the epitaxial layer is easily maintained, and therefore the substrate of the present disclosure has a very high carrier concentration. Since a large amount of impurities is added, the flatness of the surface can be maintained even if the lattice constant of the crystal deviates from that of a pure Group III nitride semiconductor crystal.

[0051] The thickness of the Group III nitride semiconductor film is more preferably 1 μm or more and 8 μm or less. If the thickness is 1 μm or more and 8 μm or less, a film having a sufficiently stable surface can be formed, and the flatness can be sufficiently maintained even if the degree of lattice mismatch between the substrate and the epitaxial layer is large.

[0052] According to the Group III nitride semiconductor epitaxial wafer, the root mean square roughness (RMS) is 10 nm or less when measured in a 50 μm square region, and in the case of use in electronic devices, a device having a low resistance at the time of operation and a small leakage current can be realized.

[0053] <Method for manufacturing Group III nitride semiconductor epitaxial wafer> The method for manufacturing the Group III nitride semiconductor epitaxial wafer according to Embodiment 1 has each of the following steps.

[0054] (1) A Group III nitride semiconductor film having a conductivity showing n-type and a carrier concentration of 10 20 cm -3 The Group III nitride semiconductor substrate described above. Note that the method for manufacturing the Group III nitride semiconductor substrate based on the OVPE method can be performed by ordinary conditions.

[0055] (2) The surface of the obtained Group III nitride semiconductor substrate is polished to obtain a Group III nitride semiconductor substrate having a surface in which the deviation angle formed by the normal line and the c-axis of the Group III nitride semiconductor substrate described above is 0.38 degrees or more and 0.6 degrees or less. The procedure for obtaining a Group III nitride semiconductor substrate having a surface in which the deviation angle is 0.38 degrees or more and 0.6 degrees or less is described later.

[0056] (3) A Group III nitride semiconductor film is epitaxially grown on the surface of the Group III nitride semiconductor substrate having a misalignment angle of 0.38 degrees or more and 0.6 degrees or less. For example, the Group III nitride semiconductor film can be epitaxially grown by a metal organic vapor phase epitaxy (MOVPE) method. Note that the method of epitaxial growth is not limited to the metal organic vapor phase epitaxy (MOVPE) method.

[0057] According to the above, a Group III nitride semiconductor epitaxial wafer can be obtained.

[0058] <Process of obtaining a Group III nitride semiconductor substrate having a surface with a misalignment angle of 0.38 degrees or more and 0.6 degrees or less> In the process of polishing the Group III nitride semiconductor substrate, the Group III nitride semiconductor substrate is placed so that the angle formed by the normal line of the polishing surface, i.e., the imaginary polishing surface, and the c-axis of the Group III nitride semiconductor substrate has a tilt of 0.38 degrees or more and 0.6 degrees or less. The imaginary polishing surface can also be a horizontal surface. Alternatively, it is not limited to a horizontal surface, and can also be a vertical surface.

[0059] In addition, in a general Group III nitride semiconductor substrate, a c-plane, in which the c-axis is the normal line, appears on the surface. Therefore, in the case where the c-plane of the surface of the Group III nitride semiconductor substrate to be placed is a horizontal surface, the c-plane to be placed is tilted with respect to the horizontal surface. Therefore, the Group III nitride semiconductor substrate can be placed on a jig having a surface whose normal line has a tilt of 0.38 degrees or more and 0.6 degrees or less with respect to the vertical direction.

[0060] Then, the surface of the Group III nitride semiconductor substrate is polished to be parallel to the polishing surface. Thereby, a Group III nitride semiconductor substrate having a misalignment angle of 0.38 degrees or more and 0.6 degrees or less between the normal line of the surface and the c-axis can be obtained.

[0061] <Electronic device> In the electronic device, the above Group III nitride semiconductor epitaxial wafer can be used. Thereby, a device having low resistance and small leakage current at the time of operation can be realized.

[0062] (Example) In this example, as the Group III nitride semiconductor substrate, a gallium nitride substrate manufactured by an OVPE method is used, and a gallium nitride film as a Group III nitride semiconductor film is formed by a metal organic vapor phase epitaxy (MOVPE) method.

[0063] The gallium nitride substrate has an oxygen concentration of 1 x 10 21 atoms cm -3 , is n-type, and has a carrier concentration of 2 x 10 20 cm-3 A substrate with a thickness of 400 μm was used. The deviation angle was varied from 0.383 degrees to 0.584 degrees. A gallium nitride film was incorporated into silicon as a dopant element, exhibiting n-type dopant with a carrier concentration of 2 × 10⁻⁶. 16 cm -3 The thickness was 8 μm. After the gallium nitride film was formed, the surface condition was evaluated using atomic force microscopy (AFM). In addition, the RMS value of a 50 μm square area was measured.

[0064] Figure 2 Images (a) to (f) are differential interference microscope images of gallium nitride film surfaces obtained from group III nitride semiconductor substrates with different offset angles in this embodiment. Figure 3 (a) to (f) are atomic force microscopy (AFM) images with a viewing angle of 90 μm in the examples.

[0065] exist Figure 2 In the differential interference microscope images, it can be seen that the surface is flat when the deviation angle is (c) 0.415 degrees, (d) 0.473 degrees, and (e) 0.514 degrees. Furthermore, in Figure 3 In the atomic force microscope images, it can be seen that when the deviation angle is (c) 0.415 degrees, (d) 0.473 degrees, and (e) 0.514 degrees, the difference between light and dark is relatively small and the surface is flat.

[0066] Depend on Figure 2 and Figure 3 It can be confirmed that if the deviation angle is greater than 0.4 degrees and less than 0.5 degrees, the surface of the epitaxial film after formation is relatively flat in the differential interference microscope image. Furthermore, it can be confirmed by the atomic force microscope image (AFM image) that a flat film is formed that suppresses RMS to less than 5 nm.

[0067] (Comparative example) In the comparative example, a gallium nitride substrate manufactured by the HVPE method was used as the group III nitride semiconductor substrate, and a gallium nitride film was formed by the MOVPE method in the same manner as in the example.

[0068] The gallium nitride substrate uses an n-type substrate with a carrier concentration of 2 × 10⁻⁶. 18 cm -3 A substrate with a thickness of 400 μm was used. The deviation angle was varied from 0.355 degrees to 0.611 degrees. For gallium nitride films, silicon was introduced as a dopant element, resulting in an n-type film with a carrier concentration of 2 × 10⁻⁶. 16 cm -3 The thickness was 8 μm. After the gallium nitride film was formed, the surface condition was evaluated using atomic force microscopy (AFM) in the same manner as in the example. In addition, the RMS value of a 50 μm square area was measured.

[0069] Figure 4 (a) to (e) are differential interference microscope images of the surface of a gallium nitride film obtained from a Group III nitride semiconductor substrate having different misorientation angles in a comparative example, Figure 5 (a) to (e) are atomic force microscope images (AFM images) of a view angle of 90 μm in a comparative example.

[0070] From Figure 4 and Figure 5 It can be confirmed that the Group III nitride film produced on a substrate having a low impurity concentration is relatively flat in the differential interference microscope image of the surface at any misorientation angle, and further, it can be confirmed from the atomic force microscope image (AFM image) that a flat film having an RMS of 5 nm or less can be formed in a wide range of 0.4 degrees or more of the misorientation angle.

[0071] Figure 6 is a graph showing the relationship between the surface roughness and the misorientation angle of the substrate in the examples and the comparative example. As shown in Figure 6 , it can be confirmed that in the comparative example, the misorientation angle of 0.4 degrees or more is sufficient to make the RMS value 5 nm or less. On the other hand, in the examples, it can be confirmed that the range of the misorientation angle of 0.38 to 0.6 degrees is sufficient to make the RMS value 10 nm or less, and to make the RMS value 5 nm or less, it is necessary to suppress the misorientation angle to a narrow range of 0.4 to 0.55 degrees.

[0072] It is confirmed that in a substrate having a high impurity concentration, a large effect is imparted to the improvement of flatness in a narrow region in which the misorientation angle is limited.

[0073] Industrial applicability As described above, according to the Group III nitride semiconductor epitaxial wafer of the present disclosure, a flat Group III nitride semiconductor epitaxial film can be formed, and thus the leakage current of an electronic device having a low on-resistance can be reduced, and an improvement in reliability can be expected.

Claims

1. A group III nitride semiconductor epitaxial wafer, comprising: A group III nitride semiconductor substrate exhibiting n-type conductivity with a carrier concentration of 10. 20 cm -3 The above; and A group III nitride semiconductor film, comprising an epitaxial layer epitaxially grown on the group III nitride semiconductor substrate. The thickness of the group III nitride semiconductor film is greater than 1 μm and less than 30 μm. In the group III nitride semiconductor substrate, the deviation angle between the normal of the surface of the group III nitride semiconductor substrate on which the group III nitride semiconductor film is formed and the c-axis of the group III nitride semiconductor substrate is 0.38 degrees or more and 0.6 degrees or less.

2. The group III nitride semiconductor epitaxial wafer according to claim 1, wherein, The root mean square roughness (RMS) of the surface of the group III nitride semiconductor film, measured in 50 μm square, is less than 10 nm.

3. The group III nitride semiconductor epitaxial wafer according to claim 2, wherein, The root mean square roughness (RMS) of the surface of the group III nitride semiconductor film with a surface area of ​​50 μm is less than 5 nm, and the deviation angle between the normal of the surface of the group III nitride semiconductor substrate and the c-axis of the group III nitride semiconductor substrate is more than 0.4 degrees and less than 0.55 degrees.

4. The group III nitride semiconductor epitaxial wafer according to any one of claims 1 to 3, wherein, The n-type doping element of the group III nitride semiconductor substrate is oxygen.

5. The group III nitride semiconductor epitaxial wafer according to any one of claims 1 to 3, wherein, The main Group III element in the Group III nitride semiconductor substrate is gallium.

6. The group III nitride semiconductor epitaxial wafer according to claim 5, wherein, The oxygen concentration in the group III nitride semiconductor substrate is 4.4 × 10⁻⁶. 20 atoms·cm -3 above.

7. The group III nitride semiconductor epitaxial wafer according to any one of claims 1 to 3, wherein, The group III nitride semiconductor film includes an epitaxial layer with a carrier concentration lower than that of the group III nitride semiconductor substrate.

8. The group III nitride semiconductor epitaxial wafer according to any one of claims 1 to 3, wherein, The group III nitride semiconductor film contains a carrier concentration of 5 × 10⁻⁶. 16 cm -3 The following epitaxial layers.

9. The group III nitride semiconductor epitaxial wafer according to any one of claims 1 to 3, wherein, The thickness of the group III nitride semiconductor film is greater than 1 μm and less than 8 μm.

10. A device that uses the group III nitride semiconductor epitaxial wafer described in any one of claims 1 to 3.

11. A method for manufacturing a group III nitride semiconductor epitaxial wafer, comprising: The process of forming a group III nitride semiconductor substrate using the OVPE method, wherein the group III nitride semiconductor substrate exhibits n-type conductivity and a carrier concentration of 10. 20 cm -3 above; The process of grinding the surface of the obtained group III nitride semiconductor substrate to obtain a group III nitride semiconductor substrate having a surface whose normal to the c-axis of the group III nitride semiconductor substrate has an angle of deviation of 0.38 degrees or more and 0.6 degrees or less; and The process of epitaxially growing a group III nitride semiconductor film on the surface of the group III nitride semiconductor substrate with an offset angle of 0.38 degrees or more and 0.6 degrees or less.

12. The method for manufacturing a group III nitride semiconductor epitaxial wafer according to claim 11, wherein, In the process of polishing the group III nitride semiconductor substrate, the group III nitride semiconductor substrate is placed in an inclination such that the angle between the normal of the polished plane (i.e., the imaginary polished surface) and the c-axis of the group III nitride semiconductor substrate is 0.38 degrees or more and 0.6 degrees or less. The surface of the group III nitride semiconductor substrate is polished to be parallel to the polished surface, resulting in a group III nitride semiconductor substrate in which the deviation angle between the surface normal and the c-axis is 0.38 degrees or more and 0.6 degrees or less.

Images