HVPE GaN and AlGaN "substrates" for homoepitaxy

We are developing GaN, AIN, and AlGaN hydride vapor phase epitaxy (HVPE) to produce substrate materials for subsequent III-V nitride homoepitaxy. Two types of the substrates under development are (1) thin nitride layers on SIC substrates and (2) free-standing GaN platelets. For the first type, GaN, AlN and AlxGa1-xN (x similar to 0.5) layers were grown by HVPE on SiC substrates without any buffer layer, Some of AlGaN layers were deposited on GaN initial layers grown on SiC in the same epitaxial run. The structural, optical and electrical properties of these layers were investigated. As for the second type of the substrates, we grow thick GaN layers on SiC substrates and remove SIC substrate after the growth by dry etching. The surfaces of these bulk GaN crystals had high structural quality and good planarity, which was obtained without mechanical treatment.