Lateral overgrowth of GaN on patterned GaN/sapphire substrate via selective metal organic vapour phase epitaxy: a route to produce self supported GaN substrates

Abstract

In the present paper we propose to extend the selective epitaxy of GaN to the lateral overgrowth and to take advantage of the growth anisotropy to produce strain free GaN crystals. After filling the openings in a dielectric mask by selective epitaxy, lateral overgrowth occurs reflecting the growth anisotropy. This allows the fabrication of samples with non-planar geometry. The selective epitaxy was achieved by metal organics vapour phase epitaxy (MOVPE) whereas lateral overgrowth until island coalescence was carried out either by MOVPE or halide vapour phase epitaxy (HVPE). A GaN epitaxial layer is first grown using atmospheric pressure metalorganic vapour phase epitaxy on {0001} sapphire. The dielectric film is silicon nitride. The openings are achieved using standard photolithographic technology. These openings reveal free GaN surface and are used for epitaxial regrowth by MOVPE, and then by HVPE.