A study was made of the surface morphology and dislocation structure of InAs which had been grown onto GaAs or InP substrates, and of GaSb which had been grown onto GaAs substrates, by means of metalorganic chemical vapor deposition. Atomic force microscopy was used to determine threading dislocation densities by studying singularities in the atomic terrace structure. All of the layers included a 100nm buffer which was grown at 400C. It was noted that this greatly improved the surface morphology for all of the material combinations which were studied. The lowest dislocation densities were found in thick GaSb layers on GaAs; with a density of about 106cm2 in a 5 layer. Slightly higher levels (5 x 106/cm2) were observed in InAs, but the surface roughness was much lower. In all of the samples, the limiting factor for surface roughness was found to be the formation of hillocks that consisted of growth spirals which were centered on dislocations.

S.P.Watkins, R.Arès, G.Soerensen, W.Zhong, C.A.Tran, J.E.Bryce, C.R.Bolognesi: Journal of Crystal Growth, 1997, 170, 788-93