High-resolution X-ray diffraction, high-resolution X-ray topographic and transmission electron microscopic data indicated that, for a given channel layer thickness, the misfit dislocation density was always lower in high electron-mobility transistor structures which had been grown onto substrates with lower threading dislocation densities. It was also noted that the onset of misfit dislocation formation occurred at higher channel layer thicknesses in the case of high electron-mobility transistor structures which had been grown onto substrates with lower threading dislocation densities. However, the ratio of misfit dislocations to threading dislocations was greater than unity in substrates with a low dislocation density. This demonstrated that other misfit dislocation nucleation sources (such as surface particles) were important when there was an insufficient density of threading dislocations.

M.Meshkinpour, M.S.Goorsky, B.Jenichen, D.C.Streit, T.R.Block: Journal of Applied Physics, 1997, 81[7], 3124-8