Effect of refined nitridation of sapphire substrates in hydride vapor phase epitaxy: Definite correlation of structural characteristics between a low-temperature-grown buffer layer and a subsequent high-temperature-grown layer of GaN

The effect of refined nitridation of sapphire substrates on the characteristics of GaN layers subsequently grown by using hydride vapor phase epitaxy (HVPE) was investigated. When lowtemperature-grown (LTG) GaN buffer layers were grown on nitridated sapphire substrates in a refined way, the structural characteristics of the LTG GaN layers were found to be transferred to the subsequent high-temperature-grown (HTG) GaN layers. This result implies that well-controlled nitridation of sapphire substrates plays an important role and that the quality of the HTG GaN layer can be rationally controlled by monitoring the characteristics of a LTG GaN buffer layer when it is grown on a properly nitridated sapphire substrate.