The melt-back etching effect of the residual Ga in the reactor for GaN grown on (111) Si

The reaction between gallium (Ga) and silicon (Si), termed melt-back etching, greatly deteriorates the quality of GaN grown on a Si substrate. In this paper, the mechanism of melt-back etching was investigated layer-by-layer in a GaN/AlN/Si system. It is found that the environment of the reactor plays a critical role in melt-back etching, which may happen as early as during the baking process. Drawing on experimental evidence and analyses, a two-step melt-back etching model is proposed. Finally, optimized pretreatments including an AlN precoating process and reduction in baking temperature were used to successfully solve the etching problem and verify the model. (C) 2022 Author(s).