GaN COMPOSITE SUBSTRATE AND GaN SELF-SUPPORTING SUBSTRATE, AND PREPARATION METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a GaN composite substrate and a GaN self-supporting substrate in which dislocation is reduced as compared to the conventional ones.SOLUTION: A preparation method for a GaN composite substrate 10 includes: an alumina layer forming step of forming a polycrystalline alumina layer on a template substrate formed by epitaxially forming a GaN layer 2 on a ground substrate 1 so as to make a (0001) plane parallel with the substrate surface; a communication recession forming step of discretely forming a plurality of openings 3h on the polycrystalline alumina layer and forming a plurality of recessions 2h each communicating with each of the plurality of openings 3h on the GaN layer 2, thereby forming a plurality of communication recessions H in each of which one opening 3h and one recession 2h communicate with each other; and a thick film layer forming step of setting the polycrystalline alumina layer having the plurality of openings 3h formed therein as a mask layer 3 and setting the GaN layer 2 having the plurality of recessions 2h formed therein as a seed crystal layer, and then, while making the plurality of recessions 2h as starting points of growth, forming a GaN thick film layer 4 covering the entire upper surface of the mask layer 3 by the Na flux method.SELECTED DRAWING: Figure 1