| 摘要 |
A GaN layer 31 is 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 base 1. Subsequently, a GaN layer 32 is 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 1), and then epitaxial growth is effected in the vertical direction. In this case, propagation of threading dislocations contained in the GaN layer 31 can be prevented in the upper portion of the GaN layer 32 that is formed through lateral epitaxial growth. Thereafter, the remaining GaN layer 31 is removed through etching, together with the GaN layer 32 formed atop the GaN layer 31, and subsequently, a GaN layer 33 is 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 layer 32, thereby producing a GaN substrate 30 in which threading dislocations are considerably suppressed. When the area of a portion of the GaN layer 31 at which the GaN substrate 30 is in contact with the substrate base 1 is reduced, separation of the GaN substrate 30 from the substrate base 1 is readily attained.
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