Epitaxial substrate for semiconductor elements, semiconductor element, and manufacturing method for epitaxial substrates for semiconductor elements

A semiconductor element, comprising:

• a semi-insulating free-standing substrate formed of GaN being doped with Zn;
• a buffer layer formed of group 13 nitride to be adjacent to said free-standing substrate;
• a channel layer formed of group 13 nitride to be adjacent to said buffer layer;
• a barrier layer formed of group 13 nitride on an opposite side of said buffer layer with said channel layer therebetween;
• and
• a gate electrode, a source electrode, and a drain electrode being provided on said barrier layer, wherein
• part of a first region consisting of said free-standing substrate and said buffer layer is a second region containing Si at a concentration of 1×1017 cm−3 or more, and a minimum value of a concentration of Zn in said second region is 1×1017 cm−3.

A method of manufacturing an epitaxial substrate for semiconductor elements, comprising:

• a) a preparation step of preparing a semi-insulating free-standing substrate formed of GaN being doped with Zn;
• b) a buffer layer formation step of forming a buffer layer formed of group 13 nitride adjacent to said free-standing substrate;
• c) a channel layer formation step of forming a channel layer formed of group 13 nitride adjacent to said buffer layer;
• and
• d) a barrier layer formation step of forming a barrier layer formed of group 13 nitride in a position opposite to said buffer layer with said channel layer therebetween, wherein
• a second region containing Si at a concentration of 1×1017 cm−3 or more is formed through taking Si in said free-standing substrate, which has been prepared in said preparation step, from outside before said buffer layer formation step is completed, in part of a first region consisting of said free-standing substrate and said buffer layer, and
• in said buffer layer formation step, Zn is diffused from said free-standing substrate, thereby forming said buffer layer in which a minimum value of a concentration of Zn is 1×1017 cm−3 in said second region.