Detailed study of effects of duration of pre-AIN-growth trimethylaluminum step on morphologies of GaN layers grown on silicon substrate by metal organic chemical vapor deposition

In this study, we investigate how the duration of trimethylaluminum (TMAI) flow steps used before aluminum nitride (AIN) growth affects the crystal quality of an AIN layer and, in turn, the surface morphologies of a gallium nitride (GaN) layer in a GaN-on-AIN-on-silicon (111) structure A high pit density was observed on a GaN surface grown under an incorrect pre-AIN-growth TMAI step duration Transmission electron microscopy revealed that crystallographically inclined AIM crystals were contained in the AIM layer grown after the duration and that these crystals impeded the GaN layer from growing. When the pre-AIN-growth TMAI step duration was short, a high density of dislocations was generated in the AIN layer, and polycrystalline growth began on the AIN surface. When the duration was long, an excessive amount of aluminum reacted with silicon, forming a silicon-aluminum alloy, and the AIN layer grown on this alloy contained crystallographically inclined crystals. (C) 2018 The Japan Society of Applied Physics