Group III nitride crystal substrate, epilayer-containing group III nitride crystal substrate, semiconductor device and method of manufacturing the same
A group III nitride crystal substrate is provided in which a uniform distortion at a surface layer of the crystal substrate represented by a value of |d 1 −d 2 | /d 2 obtained from a plane spacing d 1 at the X-ray penetration depth of 0.3 μm and a plane spacing d 2 at the X-ray penetration depth of 5 μm is equal to or lower than 1.9 ×10 −3 , and the main surface has a plane orientation inclined in the <10-10> direction at an angle equal to or greater than 10° and equal to or smaller than 80° with respect to one of (0001) and (000-1) planes of the crystal substrate. A group III nitride crystal substrate suitable for manufacturing a light emitting device with a blue shift of an emission suppressed, an epilayer-containing group III nitride crystal substrate, a semiconductor device and a method of manufacturing the same can thereby be provided.
1. A group III nitride crystal substrate, wherein,
a plane spacing of arbitrary specific parallel crystal lattice planes of said crystal substrate being obtained from X-ray diffraction measurement performed with variation of X-ray penetration depth from a main surface of said crystal substrate while X-ray diffraction conditions of said specific parallel crystal lattice planes of said crystal substrate are satisfied,
a uniform distortion at a surface layer of said crystal substrate represented by a value of |d 1 −d 2 |/d 2 obtained from a plane spacing d 1 at said X-ray penetration depth of 0.3 μm and a plane spacing d 2 at said X-ray penetration depth of 5 μm is equal to or lower than 1.9×10 −3 , and
said main surface has a plane orientation inclined in a <10-10> direction at an angle equal to or greater than 10° and equal to or smaller than 80° with respect to one of (0001) and (000-1) planes of said crystal substrate.
2. The group III nitride crystal substrate according to claim 1 , wherein said main surface has a surface roughness Ra of 3 nm or lower.
3. The group III nitride crystal substrate according to claim 1 , wherein said main surface has a plane orientation inclined at an angle falling within ±4° with respect to any of {20-21}, {10-11}, {20-2-1}, and {10-1-1} planes of said crystal substrate.
4. The group III nitride crystal substrate according to claim 3 , wherein said main surface has a plane orientation inclined at an inclination angle having an absolute value of less than 0.1° with respect to any of the {20-21}, {10-11}, {20-2-1}, and {10-1-1} planes of said crystal substrate so as to be substantially parallel thereto.
5. The group III nitride crystal substrate according to claim 3 , wherein said main surface has a plane orientation inclined at an inclination angle having an absolute value of equal to or more than 0.1° and equal to or less than 4° with respect to any of the {20-21}, {10-11}, {20-2-1}, and {10-1-1} planes of said crystal substrate.
6. The group III nitride crystal substrate according to claim 1 , wherein oxygen present at said main surface has a concentration of equal to or more than 2 at. % and equal to or less than 16 at. %.
7. The group III nitride crystal substrate according to claim 1 , wherein a dislocation density at said main surface is equal to or less than 1 ×10 7 cm −2 .
8. The group III nitride crystal substrate according to claim 1 , having a diameter equal to or more than 40 mm and equal to or less than 150 mm.
9. The group III nitride crystal substrate according to claim 1 , wherein said specific parallel crystal lattice planes are not parallel to said main surface, and is parallel to any of (10-10), (10-11), (10-13), (11-20), (11-22), (11-24), (10-1-1), (10-1-3), (11-2-2), and (11-2-4) planes.