Single step process for epitaxial lateral overgrowth of GaN on SiC and sapphire substrates

Using flow modulation organometallic vapor phase epitaxy, a process has bee n developed which produces epitaxial lateral overgrowth of GaN-base materia ls directly on SiC and sapphire substrates patterned with silicon nitride. The key feature of this single step process is the use of a high temperatur e AlGaN nucleation layer which wets the exposed substrate surface, without significant nucleation on the mask. This eliminates the need for regrowth w hile producing smooth growth surfaces in the window opening as well as over the mask. Subsequent GaN deposition results in relatively defect free mate rials grown laterally over the mask. Using arrays of stripe windows aligned parallel to the < 1 (1) under bar 00 > crystal direction, the epitaxial fi lms completely planarize after roughly 5 microns of growth. Defect densitie s estimated from atomic force micrographs indicate a reduction from mid 10( 8) to 10(5) cm(-2) in regions over the window and over the mask, respective ly. This process represents a significant simplification over currently use d regrowth methods for obtaining low defect density laterally overgrown GaN materials. (C) 1999 American Institute of Physics. [S0003-6951(99)00250-8] .