Method for fabricating group iii nitride compound semiconductor substrates and semiconductor devices

Abstract

A GaN layeris subjected to etching, so as to form an island-like structure having, for example, a dot, stripe, or grid shape, thereby providing a trench/mesa structure including mesas and trenches whose bottoms sink into the surface of a substrate baseSubsequently, a GaN layeris lateral-epitaxially grown with the top surfaces of the mesas and sidewalls of the trenches serving as nuclei, to thereby fill upper portions of the trenches (depressions of the substrate base), and then epitaxial growth is effected in the vertical direction. In this case, propagation of threading dislocations contained in the GaN layercan be prevented in the upper portion of the GaN layerthat is formed through lateral epitaxial growth. Thereafter, the remaining GaN layeris removed through etching, together with the GaN layerformed atop the GaN layerand subsequently, a GaN layeris lateral-epitaxially grown with the top surfaces of mesas and sidewalls of trenches serving as nuclei, the mesas and trenches being formed of the remaining GaN layerthereby producing a GaN substratein which threading dislocations are considerably suppressed. When the area of a portion of the GaN layerat which the GaN substrateis in contact with the substrate baseis reduced, separation of the GaN substratefrom the substrate baseis readily attained.