Metal–Organic Vapor Phase Epitaxy of High‐Quality GaN on Al‐Pretreated Sapphire Substrates Without Using Low‐Temperature Buffer Layers

Metal–organic vapor phase epitaxy of GaN on sapphire (0001) substrates without using low‐temperature (LT) buffer layers is demonstrated. The growth of GaN is achieved by pretreatment of sapphire with trimethylaluminum (TMA) at a high temperature (1050 °C) in a H2 + N2 gas mixture. The TMA pretreatment forms AlN, which acts as nucleation seeds for the subsequent growth of GaN at the same temperature. When AlN created by the TMA pretreatment is three‐dimensional, similar to conventional LT buffer layers, the GaN layers exhibit good structural properties such as atomically smooth surfaces and narrow X‐ray diffraction line widths, comparable to those of GaN on LT buffer layers. In addition, the growth evolution of GaN on TMA‐pretreated sapphire is similar to that on GaN or AlN LT buffer layers. These similarities between the TMA pretreatment and conventional LT buffer‐layer technologies might offer an opportunity to further generalize the heteroepitaxy growth model of GaN.