AlxGa1-xN epilayers were grown on a high temperature AlN buffer grown sapphire substrate by HVPE. The nitridation and AlN buffer growth temperature was kept constant at 1110οC and buffer layer growth time was varied from 1 min to 3 min. The effects of nitridation of the sapphire substrate and buffer layer thickness on the morphological, structural and optical properties of the AlxGa1-xN layers were investigated. The crystal quality of AlxGa1-xN epilayers that were grown on the high temperature AlN buffer layer were better than that grown on the nitridated sapphire substrate. In addition, crystal quality improved when the buffer layer thickness changed from 162 to 205 nm, but was degraded when the buffer layer thickness was increased to 267 nm. These results indicate that an optimal AlN buffer layer thickness of approximately 200 nm is required for minimizing threading dislocations.

Keywords: A1. Growth time, A3. HVPE, B1. AlGaN, B1. AlN, B1. Buffer.