III nitride semiconductor substrate, epitaxial substrate, and semiconductor device
In a semiconductor device 100 , it is possible to prevent C from piling up at a boundary face between an epitaxial layer 22 and a group III nitride semiconductor substrate 10 by the presence of 30×10 10 pieces/cm 2 to 2000×10 10 pieces/cm 2 of sulfide in terms of S and 2 at % to 20 at % of oxide in terms of O in a surface layer 12 . By thus preventing C from piling up, a high-resistivity layer is prevented from being formed on the boundary face between the epitaxial layer 22 and the group III nitride semiconductor substrate 10 . Accordingly, it is possible to reduce electrical resistance at the boundary face between the epitaxial layer 22 and the group III nitride semiconductor substrate 10 , and improve the crystal quality of the epitaxial layer 22 . Consequently, it is possible to improve the emission intensity and yield of the semiconductor device 100.
1. A group III nitride semiconductor substrate used in a semiconductor device, comprising a surface layer on a surface of the group III nitride semiconductor substrate, wherein
a content of carbon compound in the surface layer is 22 atomic percentage or less of carbon, and
a surface roughness of the surface layer is 5 nm or less on an RMS basis.
2. The group III nitride semiconductor substrate according to claim 1 , wherein an inclination angle of a normal axis of the surface with respect to a c-axis is 10° to 81°.
3. The group III nitride semiconductor substrate according to claim 1 , wherein a plane orientation of the surface is one of a {20-21} plane, a {10-11} plane, a {20-2-1} plane, a {10-1-1} plane, a {11-22} plane, a {22-43} plane, a {11-21} plane, a {11-2-2} plane, a {22-4-3} plane and a {11-2-1} plane.
4. The group III nitride semiconductor substrate according to claim 1 , wherein the surface layer contains 30×10 10 pieces/cm 2 to 2000×10 10 pieces/cm 2 of sulfur and 2 atomic percentage to 20 atomic percentage of oxygen.
5. The group III nitride semiconductor substrate according to claim 1 , wherein the surface layer contains 40×10 10 pieces/cm 2 to 1500×10 10 pieces/cm 2 of sulfur.
6. The group III nitride semiconductor substrate according to claim 1 , wherein the surface layer contains 3 atomic percentage to 16 atomic percentage of oxygen.
7. The group III nitride semiconductor substrate according to claim 1 , wherein the surface layer contains 120×10 10 pieces/cm 2 to 15000×10 10 pieces/cm 2 of chlorine.
8. The group III nitride semiconductor substrate according to claim 1 , wherein the surface layer contains 100×10 10 pieces/cm 2 to 12000×10 10 pieces/cm 2 of silicon.
9. The group III nitride semiconductor substrate according to claim 1 , wherein a content of copper compound in the surface layer is 150×10 10 pieces/cm 2 or lower of copper.
10. The group III nitride semiconductor substrate according to claim 1 , wherein a dislocation density of the surface layer is 1×10 6 pieces/cm 2 or lower.