III nitride semiconductor substrate, epitaxial substrate, and semiconductor device

#The present invention relates to a group III nitride semiconductor substrate, an epitaxial substrate and a semiconductor device.

#In recent years, semiconductors, including compound semiconductors, have been used in an increasingly wider range of application fields by taking advantage of various characteristic features of the semiconductors. For example, a compound semiconductor is useful as a base substrate for epitaxial layers to be laminated on, thus, the compound semiconductor is used in semiconductor devices such as a light-emitting diode (LED) and a laser diode (LD).

#If a semiconductor substrate is used as the base substrate, a surface of the semiconductor substrate needs to be processed into a strain-free mirror surface. Accordingly, preprocessing (for example, cutting, lapping and etching) is performed on a single-crystal semiconductor ingot to obtain a semiconductor substrate, and then mirror-polishing is performed on a surface of the semiconductor substrate.

#FIG. 1 is a schematic cross-sectional view illustrating a group III nitride semiconductor substrate according to a first embodiment.

#FIG. 2 is a drawing illustrating an apparatus usable in dry etching.

#FIG. 3 is a drawing illustrating an apparatus usable in polishing.

#Hereinafter, preferred embodiments of a group III nitride semiconductor substrate, an epitaxial substrate and a semiconductor device according to the present invention will be described in detail while referring to the accompanying drawings.

#(Group III Nitride Semiconductor Substrate)

#FIG. 1 is a schematic cross-sectional view illustrating a group III nitride semiconductor substrate 10 according to a first embodiment. As illustrated in FIG. 1, the group III nitride semiconductor substrate 10 (hereinafter referred to as “nitride substrate 10”) comprises a front surface 10a and a rear surface 10b opposed to each other, and a surface layer 12 is formed on the front surface 10a.