A method was presented for the reduction of threading dislocation densities, in epitaxial single layers, by accurately controlling the layer thickness. The growth of InGaAs was here restricted to less than 10 times the Matthews-Blakeslee critical thickness for which the asymmetry in [110] and [¯110] dislocation densities was greatest. Beyond this thickness, it was found that the removal or annihilation of threading dislocations in the epilayer was more than offset by the introduction of new threading dislocations from spiral and Frank-Read type sources. By keeping the epilayer thickness below this value, it was ensured that most of the misfit dislocations which were generated lay mainly in just one of the <110> directions. This reduced the likelihood of blocking by orthogonal dislocations and thus increased the mean-free-path above that which was expected in higher-density dislocation arrays. The etch-pit densities showed that the threading dislocation density could be reduced by up to an order of magnitude below that which was found in the substrate. It also reduced inhomogeneities in the distribution of threading dislocations. Atomic force microscopy showed that the surface quality of the layers remained high, and free from striations.

G.MacPherson, P.J.Goodhew: Journal of Applied Physics, 1996, 80[12], 6706-10