Growth of thin AlN nucleation layer and its impact on GaN-on-SiC heteroepitaxy

Abstract

Abstract AlN nucleation layer (NL) with thickness of 35 nm was grown on semi-insulating 4H–SiC substrate by metal organic chemical vapor deposition (MOCVD). Focused on the evolutions of the surface microstructural morphology and crystalline quality, the growth mechanism of the thin NL was studied by series of growth procedures. As interval supply of ammonia (NH3) and alternative supply of Trimethylaluminum (TMA)/NH3 are applied to NL growth, complete coalescence of AlN nucleate islands with a smooth surface and low density of defects is obtained. In addition, the impact of the thin NL on the subsequent GaN buffer layer (BL) was also discussed. Overgrown on the well-coalesced NL, surface roughening and three-dimensional mode get predominant at the initial GaN growth, which facilitates high crystalline quality of GaN BL with low wafer bow.