A TEM evaluation of ELOG GaN grown on AlN buffer layer by HVPE on (0001) 6H-SiC

The misfit between GaN and 6H-SiC is 3.5% instead of 16% on growth over sapphire, whereas that between AIN and 6H-SiC is only 1%. Therefore, ELOG GaN on AlN/6H-SiC could be a route to further improve the quality of ELOG GaN. We analyzed ELOG GaN grown on AIN at an early stage of coalescence in order to identify which dislocations bend and try to understand why. The ELOG islands were always limited by {10 (1) over bar 0} facets. From the center of these islands, more than 99% dislocations bend to the basal plane. The a-type dislocations were found to fold many times from basal to the prismatic plane, whereas when a+c dislocations bend to the basal plane, they were not seen to come back to a prismatic one.