Growth of gallium nitride by hydride vapor-phase epitaxy

This paper reviews the growth of GaN thick films by hydride vapor-phase epitaxy (HVPE). Emphasis is placed on recent developments, including the growth of nondegenerate material, characterization of film properties and suitability of such films for epitaxial device overgrowths. Films up to 74 mu m thick have been deposited on sapphire substrates with no evidence of thermally induced cracking and a room-temperature Hall mobility of 880 cm(2)/V s at 293 K. Dislocation densities have been found to decrease with film thickness to 5 x 10(7) cm(-2) or a 40 mu m thick sample. Epitaxial films overgrown on these HVPE GaN buffers, both by organometallic vapor-phase epitaxy and molecular-beam epitaxy, replicate the defect structure of the HVPE buffer, resulting in dislocation densities no higher than the HVPE buffer and lower than are typically observed for nitride epilayers grown an other substrate materials. Efforts towards film/substrate separation will be discussed.