Group III nitride semiconductor substrate and manufacturing method thereof
A method of manufacturing a group III nitride semiconductor substrate includes the growth step of epitaxially growing a first group III nitride semiconductor layer on an underlying substrate, and the process step of forming a first group III nitride semiconductor substrate by cutting and/or surface-polishing the first group III nitride semiconductor layer. In the growth step, at least one element selected from the group consisting of C, Mg, Fe, Be, Zn, V, and Sb is added as an impurity element by at least 1×10 17 cm −3 to the first group III nitride semiconductor layer. A group III nitride semiconductor substrate having controlled resistivity and low dislocation density and a manufacturing method thereof can thus be provided.
1. A group III nitride semiconductor substrate containing at least one element selected from the group consisting of O, Si, S, Ge, Se, and Te as an impurity element in concentration of at least 1×10 17 cm −3 wherein:
in-plane distribution of the concentration of said impurity element represented as a ratio of a maximum concentration to a minimum concentration of said impurity element in a main surface of the substrate is in a range from at least 1 to at most 3,
said group III nitride semiconductor substrate has resistivity of at most 1Ω·cm and thickness of at least 70 μm, and
said group III nitride semiconductor substrate is epitaxially grown on another group III nitride semiconductor substrate containing at least one element selected from the group consisting of C, Mg, Fe, Be, Zn, V, and Sb as another impurity element in concentration of at least 1×10 17 cm −3 , wherein:
in-plane distribution of the concentration of said another impurity element represented as a ratio of a maximum concentration to a minimum concentration of said another impurity element in a main surface of the substrate is in a range from at least 1 to at most 3, and
said another group III nitride semiconductor substrate has resistivity of at least 1×10 4 Ω·cm and thickness of at least 70 μm.
2. The group III nitride semiconductor substrate according to claim 1 , wherein average dislocation density is at most 1×10 7 cm −2 , and surface density of a dislocation-concentrated region where dislocation density exceeds 1×10 8 cm −2 is at most 1 cm −2 .
3. The group III nitride semiconductor substrate according to claim 1 , wherein said group III nitride is GaN.
4. The group III nitride semiconductor substrate according to claim 1 , wherein said main surface of said group III nitride semiconductor substrate is at an angle in a range from at least −5° to at most 5° with respect to any one of a (0001) surface, a (1-100) surface and a (11-20) surface.
5. The group III nitride semiconductor substrate according to claim 1 , wherein a half-width of a rocking curve in X-ray diffraction is in a range from at least 10 arcsec to at most 500 arcsec.
6. The group III nitride semiconductor substrate according to claim 1 , wherein carrier density is in a range from at least 1×10 17 cm 3 to at most 1×10 20 cm −3 .
7. The group III nitride semiconductor substrate according to claim 1 , wherein absorption coefficient for light of a wavelength of 450 nm is at most 10 cm −1 .