The growth of crack-free AlxGa1-xN layers, where x ranged from 0.133 to 0.1, which had a low dislocation density was investigated by using AlGaN/GaN heterostructures. It was found that, although the number of defects in an underlying AlGaN layer grown onto a low-temperature GaN buffer increased with increasing AlN molar fraction, the use of a highly strained AlGaN/GaN/AlGaN heterostructure on the underlying layer was effective in reducing the number of defects near to the surface.

Study of the Growth of Crack-Free AlGaN/GaN Heterostructure with Low Dislocation Density. H.K.Cho, J.Y.Lee, S.C.Choi, G.M.Yang: Journal of Crystal Growth, 2001, 222[1-2], 104-9