AlN single crystal substrate and device

Abstract

Provided is an AlN single crystal substrate which is not susceptible to chipping if subjected to processing (grinding, polishing, cutting, etc.). This AlN single crystal substrate includes carbon atoms and rare earth atoms as impurities. When the carbon atom concentration (atoms / cm3) and the rare earth atom concentration (atoms / cm3) in the AlN single crystal substrate are taken to be CC and CRE, respectively, the relational expression 0.0010<CRE / CC<0.2000 is satisfied.

Description

[Technical Field]

[0001] The present invention relates to an AlN single crystal substrate and a device including the AlN single crystal substrate. [Background technology]

[0002] In recent years, aluminum nitride (AlN) single crystals have been attracting attention as a base substrate for deep ultraviolet light-emitting devices that use AlN-based semiconductors. For example, AlN and AlGaN are used as AlN-based semiconductors. These AlN-based semiconductors have a direct transition band structure, making them suitable for light-emitting devices, and can be applied to deep ultraviolet light-emitting diodes (LEDs) and laser diodes (LDs) that can be used for sterilization and other purposes.

[0003] In such a light-emitting device, in order to achieve high transmittance in the ultraviolet region, it is desirable that the impurity concentration in the base substrate is low. For example, Patent Document 1 (Japanese Patent No. 6080148) describes an AlN single crystal containing oxygen atoms and carbon atoms, in which the concentration of oxygen atoms is 5×10 17 cm -3 5x10 or more 18 cm -3 and the concentration of carbon atoms is 4×10 17 cm -3 Over 4×10 18 cm -3 or less, and discloses an AlN single crystal in which the oxygen atom concentration is higher than the carbon atom concentration. This document states that, in order to reduce the amount of impurities, advanced control and special equipment are required during single crystal growth, and that the single crystal in which the oxygen and carbon atom concentrations are controlled has good ultraviolet light transmittance. Furthermore, Patent Document 2 (JP 2009-78971 A) describes the composition of AlN and the 17 cm -3 The total impurity density and the 50 cm -1 An AlN single crystal substrate is disclosed having the following absorption coefficients:

[0004] Regarding impurities in AlN single crystals, Patent Document 3 (Japanese Patent No. 4811082) discloses an n-type AlN crystal having a structure in which some of the Al atoms in the AlN crystal are substituted with a group IIIa element and / or a group IIIb element, and one of the adjacent N atoms is simultaneously substituted with an O atom, where the group IIIa element and / or the group IIIb element are one or more elements selected from the group consisting of Y, Sc, La, Ce, and Ga. This document describes the relationship between the total concentration of the group IIIa element and / or the group IIIb element and the oxygen concentration. Patent Document 4 (Japanese Patent No. 6932995) also discloses an AlN single crystal having a wurtzite crystal structure and a boron content of 0.5 ppm by mass or more and 251 ppm by mass or less. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6080148 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-78971 [Patent Document 3] Patent No. 4811082 [Patent Document 4] Patent No. 6932995 Summary of the Invention

[0006] As mentioned above, in order to control the properties of AlN single crystals, such as achieving high deep-ultraviolet light transmittance and n-type conductivity, it is conceivable to control the amount of impurities present in the AlN single crystal. However, AlN single crystal substrates such as those disclosed in Patent Documents 1 to 4 are prone to chipping (defects such as chips and cracks) when processed (grinding, polishing, cutting, etc.), which results in a problem of reduced yield. Therefore, it is desirable to suppress chipping that occurs in AlN single crystal substrates when processing them.

[0007] The present inventors have now discovered that, when an AlN single crystal substrate satisfies a predetermined relational expression regarding the concentration ratio of carbon atoms and rare earth atoms as impurities, chipping is less likely to occur when the substrate is processed (grinded, polished, cut, etc.).

[0008] Therefore, an object of the present invention is to provide an AlN single crystal substrate that is less likely to chip when processed (grinded, polished, cut, etc.).

[0009] According to one aspect of the present invention, there is provided an AlN single crystal substrate containing carbon atoms and rare earth atoms as impurities, the carbon atom concentration (atoms / cm) in the AlN single crystal substrate being 3 ) to C C , rare earth atomic concentration (atoms / cm 3 ) to C RE When 0.0010 <C RE / C C <0.2000 An AlN single crystal substrate is provided that satisfies the following relational expression.

[0010] According to another aspect of the present invention, there is provided a device comprising the AlN single crystal substrate. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of a heat treatment apparatus used to produce AlN raw material powder. [Figure 2] FIG. 1 is a schematic cross-sectional view showing the configuration of a crystal growth apparatus used in a sublimation method. DETAILED DESCRIPTION OF THE INVENTION

[0012] AlN single crystal substrate The AlN single crystal substrate according to the present invention contains carbon atoms and rare earth atoms as impurities. The AlN single crystal substrate has a carbon atom concentration (atoms / cm 3 ) to C C , rare earth atomic concentration (atoms / cm 3) to C RE Then, the relation is: 0.0010 <C RE / C C <0.2000. In this way, when the AlN single crystal substrate satisfies the predetermined relational expression regarding the concentration ratio of carbon atoms and rare earth atoms as impurities, chipping is less likely to occur when the substrate is processed (grinding, polishing, cutting, etc.). Therefore, by processing such an AlN single crystal substrate, AlN single crystal substrates can be manufactured with a high yield. That is, as mentioned above, conventional AlN single crystal substrates are prone to chipping when processed (grinding, polishing, cutting, etc.), resulting in a problem of reduced yield. In this regard, the AlN single crystal substrate of the present invention can advantageously solve the above problem.

[0013] The AlN single crystal substrate of the present invention has a carbon atom concentration C C and rare earth atomic concentration C RE Regarding 0.0010 <C RE / C C <0.2000, but C RE / C C The lower limit is preferably 0.0020 <C RE / C C , more preferably 0.0030 <C RE / C C The higher the lower limit, the more cracks that occur during chipping can be reduced. RE / C C The upper limit of C RE / C C <0.1000, more preferably C RE / C C <0.0100, and the lower the upper limit, the more the occurrence of chipping can be reduced. By satisfying this relationship, an AlN single crystal substrate can be obtained that is less susceptible to chipping when processed (grinding, polishing, cutting, etc.). Furthermore, by processing such an AlN single crystal substrate, AlN single crystal substrates can be manufactured with a higher yield.

[0014] The AlN single crystal substrate may contain oxygen atoms as impurities. In this case, the oxygen atom concentration (atoms / cm 3 ) to C O When this is done, it is 4.5×10 18 <C O -C C <9.0×10 21 It is preferable that the relational expression be satisfied, and more preferably 1.0 × 10 19 <C O -C C <9.0×10 20 and more preferably 1.0 × 10 19 <C O -C C <2.0×10 20 The following relation is satisfied.

[0015] In addition, when the AlN single crystal substrate contains oxygen atoms as impurities, the oxygen atom concentration (atoms / cm 3 ) to C O When this is done, it is 4.0×10 18 <C C <4.0×10 21 , 4.0×10 18 <C O <4.0×10 21 , and 1.0 × 10 16 <C RE <1.0×10 19 It is preferable that the relational expression be satisfied, and more preferably 1.0 × 10 19 <C C <4.0×10 20 , 1.0×10 19 <C O <8.0×10 20 , and 1.0 × 10 17 <C RE <1.0×10 18 and more preferably 5.0 × 10 19 <C C <1.0×10 20 , 5.0×10 19 <C O <5.0×10 20 , and 2.0 × 10 17 <C RE <7.0×1017 The following relation is satisfied.

[0016] Thus, the AlN single crystal substrate contains carbon atoms and rare earth atoms as impurities, but preferably contains oxygen atoms as impurities. Regarding the concentration of each atom in the AlN single crystal substrate, the carbon atom concentration C C (atoms / cm 3 ) is 4.0 × 10 18 <C C <4.0×10 21 is preferably 1.0×10 19 <C C <4.0×10 20 , and more preferably 5.0 × 10 19 <C C <1.0×10 20 The oxygen atom concentration C O (atoms / cm 3 ) is 4.0 × 10 18 <C O <4.0×10 21 is preferably 1.0×10 19 <C O <8.0×10 20 , and more preferably 5.0 × 10 19 <C O <5.0×10 20 The rare earth atom concentration C RE (atoms / cm 3 ) is 1.0 × 10 16 <C RE <1.0×10 19 is preferably 1.0×10 17 <C RE <1.0×10 18 , and more preferably 2.0 × 10 17 <C RE <7.0×10 17 is.

[0017] Examples of rare earth atoms contained as impurities in the AlN single crystal substrate include Y atoms, La atoms, Sm atoms, Ce atoms, Yb atoms, Eu atoms, Dy atoms, and combinations thereof. From the viewpoint of reducing chipping, the rare earth atoms are preferably Y atoms, Ce atoms, Yb atoms, Sm atoms, and combinations thereof, and more preferably Y atoms.

[0018] The surface area of ​​the AlN single crystal substrate is 75 mm 2 Exceeds 18,500mm 2 Preferably it is less than 300 mm 2 Exceeds 8200mm 2 The thickness of the AlN single crystal substrate is preferably more than 0.10 mm and less than 1.00 mm, and more preferably more than 0.30 mm and less than 0.70 mm.

[0019] The AlN single crystal substrate of the present invention is preferably an oriented layer oriented in both the c-axis and a-axis directions, and may contain mosaic crystals. Mosaic crystals are a collection of crystals that do not have clear grain boundaries but whose orientation slightly differs from one or both of the c-axis and a-axis. Such an oriented layer has a structure in which the crystal orientation is generally aligned in the approximately normal direction (c-axis direction) and the in-plane direction (a-axis direction). This structure makes it possible to form a semiconductor layer thereon with excellent quality, particularly excellent orientation. In other words, when a semiconductor layer is formed on an oriented layer, the crystal orientation of the semiconductor layer generally follows the crystal orientation of the oriented layer. Therefore, it is easy to form a semiconductor film on an AlN single crystal substrate as an oriented film.

[0020] The method for evaluating the orientation of the AlN single crystal substrate of the present invention is not particularly limited, and known analytical techniques such as EBSD (Electron Backscatter Diffraction Patterns) and X-ray pole figures can be used. For example, when using EBSD, inverse pole figure mapping and crystal orientation mapping of the surface (plate surface) of the AlN single crystal substrate or a cross section perpendicular to the plate surface are measured. The obtained inverse pole figure mapping can be defined as being oriented along two axes, the approximately normal direction and the approximately plate surface direction, when the following four conditions are met: (A) the substrate is oriented in a specific direction (first axis) approximately normal to the plate surface; (B) the substrate is oriented in a specific direction (second axis) approximately in the plate surface and perpendicular to the first axis; and (C) the tilt angles from the first axis are distributed within ±10°; and (D) the tilt angles from the second axis are distributed within ±10°. In other words, when the above four conditions are met, the substrate can be determined to be oriented along two axes, the c-axis and the a-axis. For example, if the approximately normal direction to the plate surface is oriented along the c-axis, the approximately in-plane direction may be oriented along a specific direction (e.g., the a-axis) perpendicular to the c-axis. The AlN single crystal substrate may be oriented along two axes, the approximately normal direction and the approximately in-plane direction, but it is preferable that the approximately normal direction be oriented along the c-axis. The smaller the tilt angle distribution in the approximately normal direction and / or the approximately in-plane direction, the less mosaic the AlN single crystal substrate will have, and the closer it is to zero, the closer it will be to a perfect single crystal. Therefore, from the perspective of the crystallinity of the AlN single crystal substrate, it is preferable that the tilt angle distribution be small in both the approximately normal direction and the approximately in-plane direction; for example, ±5° or less is preferable, and ±3° or less is even more preferable.

[0021] Manufacturing method The AlN single crystal substrate of the present invention has a carbon atom concentration C C and rare earth atomic concentration C REAs long as the aforementioned relationship between AlN and ZnO is satisfied, various methods can be used to produce the AlN single crystal substrate. A seed substrate may be prepared and epitaxially grown thereon, or an AlN single crystal substrate may be produced directly by spontaneous nucleation without using a seed substrate. The seed substrate used may be an AlN substrate to achieve homoepitaxial growth, or a different substrate may be used to achieve heteroepitaxial growth. While vapor-phase deposition, liquid-phase deposition, or solid-phase deposition may be used to grow the single crystal, vapor-phase deposition is preferred, and the AlN single crystal is then grown, and the seed substrate portion is then ground away, if necessary, to obtain the desired AlN single crystal substrate. Examples of vapor-phase deposition methods include various CVD (chemical vapor deposition) methods (e.g., thermal CVD, plasma CVD, MOVPE, etc.), sputtering, hydride vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), sublimation, and pulsed laser deposition (PLD), with sublimation and HVPE being preferred. Examples of liquid-phase deposition methods include solution growth (e.g., flux deposition). It is also possible to obtain an AlN single crystal substrate without directly depositing an AlN single crystal on a seed substrate by forming an oriented precursor layer, converting the oriented precursor layer into an AlN single crystal layer by heat treatment, and polishing the seed substrate. Examples of methods for forming the oriented precursor layer include aerosol deposition (AD) and supersonic plasma particle deposition (HPPD).

[0022] Although known conditions can be used for any of the above-mentioned solid-phase deposition, vapor-phase deposition, and liquid-phase deposition methods, the following describes a method for producing an AlN single crystal substrate using, for example, sublimation deposition. Specifically, the substrate is produced by (a) heat-treating AlN polycrystalline powder, (b) depositing an AlN single crystal layer, and (c) grinding off the seed substrate and polishing the surface of the AlN single crystal layer.

[0023] (a) Heat treatment of AlN polycrystalline powder This process involves heat-treating AlN polycrystalline powder to obtain AlN raw material powder. As shown in FIG. 1, AlN powder 12 is placed in a sheath 10 as a raw material for AlN single crystals and heat-treated in a N2 atmosphere. At this time, graphite powder 14 and rare earth metal oxide (Y2O3, CaO, CeO2, Yb2O3, Sm2O3, etc.) powder 15 are placed in separate crucibles 16 and 17 so as not to come into direct contact with the AlN powder 12 within the sheath 10. These crucibles 16 and 17 are large enough to be housed within the sheath 10. At this time, by appropriately adjusting the contents of graphite and rare earth metal oxide, the carbon atom concentration C C and rare earth atomic concentration C RE It is possible to produce an AlN single crystal substrate that satisfies the above-mentioned relational expressions. The pressure inside the furnace of the sheath 10 is preferably 0.1 to 10 atmospheres, more preferably 0.5 to 5 atmospheres. The heat treatment temperature is preferably 1900°C to 2300°C, more preferably 2000 to 2200°C. Preferred examples of materials that constitute the sheath and crucible include tantalum carbide, tungsten, molybdenum, and boron nitride (BN), more preferably BN.

[0024] (b) Deposition of an AlN single crystal layer This process is a process of forming an AlN single crystal film on a seed substrate in a crystal growth apparatus. An example of a crystal growth apparatus used in the sublimation method is shown in FIG. 2. The film formation apparatus 20 shown in FIG. 2 includes a crucible 22, a heat insulator 24 for insulating the crucible 22, and a coil 26 for heating the crucible 22 to a high temperature. The crucible 22 contains AlN raw material powder 28 in its lower part and includes a seed substrate 30 in its upper part on which a sublimate of the AlN raw material powder 28 is deposited. The interior of the crucible 22 is pressurized in an N2 atmosphere, and the crucible 22 is heated by the coil 26 to sublimate the AlN raw material powder 28. The pressure is preferably 10 to 100 kPa, and more preferably 20 to 90 kPa. At this time, a temperature gradient is created so that the temperature in the vicinity of the seed substrate 30 in the upper part of the crucible 22 is lower than the temperature in the vicinity of the AlN raw material powder 28 in the lower part of the crucible 22. For example, the portion of the crucible 22 near the AlN raw material powder 28 is preferably heated to 1900 to 2250°C, more preferably 2000 to 2200°C, and the portion of the crucible 22 near the seed substrate 30 is preferably heated to 1400 to 2150°C, more preferably 1500 to 2050°C. At this time, the temperature of the portion near the seed substrate 30 is preferably 100 to 500°C lower than the portion near the AlN raw material powder 28, more preferably 200 to 400°C. The heating is preferably maintained for 2 to 100 hours, more preferably 4 to 90 hours. Temperature control can be performed by measuring the temperatures of the upper and lower parts of the crucible 22 with radiation thermometers (not shown) through holes in the heat insulating material 24 covering the crucible 22 and feeding the measured temperatures back into the temperature control. In this way, a SiC single crystal is placed as the seed substrate 30, and AlN is re-precipitated on its surface to form an AlN single crystal layer 32.

[0025] (c) Grinding and removing the seed substrate and polishing the surface of the AlN single crystal layer This process includes a grinding step, which removes the seed substrate to expose the AlN single crystal layer, and a polishing step, which removes irregularities and defects on the AlN single crystal surface. Since the AlN single crystal layer fabricated using a SiC substrate as the seed substrate through steps (a) and (b) still contains residual SiC single crystals, a grinding process is performed to expose the surface of the AlN single crystal layer. Furthermore, to achieve a mirror finish on the surface of the AlN single crystal layer after deposition, the plate surface is smoothed by lapping using diamond abrasive grains, and then polished by chemical mechanical polishing (CMP) using colloidal silica or similar. In this way, an AlN single crystal substrate can be fabricated.

[0026] device Devices can also be fabricated using the AlN single crystal substrate of the present invention. That is, devices preferably equipped with an AlN single crystal substrate are provided. Examples of such devices include deep ultraviolet laser diodes, deep ultraviolet diodes, power electronic devices, high-frequency devices, heat sinks, etc. The method for fabricating devices using AlN single crystal substrates is not particularly limited, and they can be fabricated by known methods. [Example]

[0027] The present invention is further illustrated by the following examples.

[0028] Examples 1 to 17 (1) Preparation of AlN single crystal substrate (1a) Heat treatment of AlN polycrystalline powder As shown in FIG. 1 , commercially available AlN powder 12 with an average particle size of 1 μm, used as a raw material for AlN single crystals, was placed in a BN sheath 10. Commercially available graphite powder 14 with an average particle size of 1 μm was placed in a BN crucible 16 in the ratio shown in Table 1 relative to 100 parts by weight of the AlN powder, while rare earth metal oxide powder 15 was placed in a BN crucible 17 in the ratio shown in Table 1 relative to 100 parts by weight of the AlN powder. Here, graphite powder 14 and rare earth metal oxide powder 15 were used in Example 7, and rare earth metal oxide powder 15 was not used in Example 8. Furthermore, as the rare earth metal oxide powder 15, yttrium oxide powder with an average particle size of 0.1 μm was used in Examples 1 to 6 and 9 to 14, cerium oxide powder with an average particle size of 1 μm in Example 15, ytterbium oxide powder with an average particle size of 1 μm in Example 16, and samarium oxide powder with an average particle size of 3 μm in Example 17 were used. These BN crucibles 16 and 17 were placed inside the BN sheath 10 so as not to directly contact the AlN powder 12. The BN crucibles 16 and 17 were sized to fit inside the sheath 10. The BN sheath 10 was heat-treated in a graphite heater furnace at 2200°C in an N2 atmosphere at 0.1 to 10 atmospheres. In this way, the AlN polycrystalline powder was heat-treated to produce AlN raw material powder.

[0029] (1b) Deposition of AlN single crystal layer 2, a crucible 22 was used as a crystal growth vessel, and a circular SiC substrate was placed in the crucible as a base material (seed substrate) 30. The AlN raw material powder 28 prepared in (1a) above was placed in the crucible so as not to come into contact with the SiC substrate. The crucible 22 was pressurized to 50 kPa in an N atmosphere, and the portion of the crucible 22 near the AlN raw material powder 28 was heated to 2100°C by high-frequency induction heating, while the portion of the crucible 22 near the SiC substrate 30 was heated to a lower temperature (temperature difference of 200°C) and maintained at that temperature, thereby re-precipitating an AlN single crystal layer 32 on the SiC substrate 30. The maintenance time was 10 hours.

[0030] (1c) Grinding and removal of SiC substrate and polishing of AlN single crystal layer surface The SiC substrate with re-precipitated AlN obtained in (1b) above was ground using a grinding wheel with a grit size up to #2000 until the AlN single crystal was exposed, and then the surface was further smoothed by lapping using diamond abrasive grains. The surface was then mirror-finished by chemical mechanical polishing (CMP) using colloidal silica. In this way, circular AlN single crystal substrates with the surface area and thickness shown in Table 2 were produced.

[0031] (2) Evaluation of AlN single crystal substrates (2a) EBSD measurement EBSD measurements were carried out on the front and back surfaces of the AlN single crystal substrate, and it was found that the AlN crystal was oriented in both the c-axis and a-axis directions.

[0032] (2b) Concentration of each atom in the AlN single crystal substrate Dynamic secondary ion mass spectrometry (D-SIMS) was performed on the polished surface of the AlN single crystal substrate. The analyzer was a CAMECA IMS-7f, and the primary ion species was C S + The measurements were carried out at a primary acceleration voltage of 15 kV and a detection area of ​​25 μm × 25 μm. This measurement was carried out at 10 measurement points on the polished surface of the AlN single crystal substrate. These 10 measurement points were determined by (i) drawing 10 straight lines radially from the center of the substrate toward the periphery, so as to divide the circular shape of the substrate into 10 equal parts (i.e., so that the angle between adjacent lines was 36 degrees), and (ii) identifying the positions where the distance from the substrate center to each of these 10 lines was 50% of the substrate radius. At each of these 10 measurement points, the average values ​​of the carbon atom concentration, oxygen atom concentration, and rare earth atom concentration were measured at a depth of 1 to 3 μm into the substrate, and the average value of these 10 points was calculated. These average values ​​were used to determine the carbon atom concentration, C in the AlN single crystal substrate. C (atoms / cm 3 ), oxygen atom concentration C O (atoms / cm 3 ) and rare earth atomic concentration C RE (atoms / cm 3 ) and the rare earth atom concentration C REcarbon atom concentration C C Ratio to (C RE / C C ), and oxygen atom concentration C O and carbon atom concentration C C The difference (C O -C C In this measurement, the carbon atom concentration C C The detection limit is 1×10 16 atoms / cm 3 , oxygen atomic concentration C O The detection limit is 5×10 17 atoms / cm 3 , rare earth atomic concentration C RE The detection limit is 3×10 15 atoms / cm 3 If the content is below these values, the AlN single crystal substrate is deemed to contain substantially no such atoms. The results are shown in Tables 1 and 2.

[0033] (2c) Check for chipping The surfaces of the AlN single crystal substrates after grinding and polishing in (1c) above were observed under an optical microscope to check for the presence or absence of chipping with a maximum length of 50 μm or more. A total of 10 AlN single crystal substrates were produced using the same method as in (1) above, and it was determined how many of them had chipping, and they were then rated according to the evaluation criteria shown below. The results are shown in Table 2. <Evaluation criteria> - Evaluation A: 9 to 10 AlN single crystal substrates were chip-free - Evaluation B: 6 to 8 AlN single crystal substrates were chip-free - Evaluation C: 3 to 5 AlN single crystal substrates without chipping - Rating D: Chipping was observed on all AlN single crystal substrates

[0034] [Table 1]

[0035] [Table 2]

Claims

1. An AlN single crystal substrate containing carbon atoms and rare earth atoms as impurities, wherein the carbon atom concentration (atoms / cm ３ ) to C Ｃ , rare earth atomic concentration (atoms / cm ３ ) to C ＲＥ When 0.0010<C ＲＥ / C Ｃ <0.2000、 4.0×10 18 < C C < 4.0×10 21 , and 1.0×10 16 <C RE ≦1.5×10 20 An AlN single crystal substrate that satisfies the following relational expression.

2. The AlN single crystal substrate contains oxygen atoms as impurities, and the oxygen atom concentration (atoms / cm ３ ) to C Ｏ When 4.5×10 １８ <C Ｏ -C Ｃ <9.0×10 ２１ 2. The AlN single crystal substrate according to claim 1, which satisfies the following relational expression:

3. The surface area of ​​the AlN single crystal substrate is 75 mm ２ Exceeding 18,500 mm ２ 3. The AlN single crystal substrate according to claim 1, wherein the thickness of the AlN single crystal substrate is greater than 0.10 mm and less than 1.00 mm.

4. The AlN single crystal substrate contains oxygen atoms as impurities, and the oxygen atom concentration (atoms / cm ３ ) to C Ｏ When 4.0×10 １８ <C Ｃ <4.0×10 ２１ 、 4.0 x 10 １８ <C Ｏ <4.0 x 10 ２１ , and 1.0×10 １６ <C ＲＥ <1.0×10 １９ 4. The AlN single crystal substrate according to claim 1, wherein the following relational expression is satisfied:

5. 5. The AlN single crystal substrate according to claim 1, wherein the rare earth atoms are Y atoms.

6. A device comprising the AlN single crystal substrate according to any one of claims 1 to 5.

Images