Layers of InAs were grown onto (001) on-axis or misoriented GaAs substrates by means of molecular beam epitaxy. The critical thickness of each InAs layer was investigated with the aid of photoluminescence spectroscopy and transmission electron microscopy. It was shown that the critical thickness was significantly affected by the substrate misorientation. The critical thickness of InAs layers which were grown onto GaAs substrates that were misoriented toward the [11¯0] direction became thicker (5 monolayers) than the 3 monolayers of the InAs layers which were grown onto GaAs (001) substrates that were on-axis, or misoriented towards the [110] direction. Plan-view transmission electron microscopic images showed that the islands which were grown coherently did not coalesce; even when beyond the on-axis critical thickness of 3 monolayers. The strain energy was calculated by using a valence force-field model to investigate the interaction between dislocations and steps in the case of misoriented substrates. As a result, it was found that the dislocation had the minimum length above which dislocations could stably exist, and that the extra strain energy which was generated at the crossing points of dislocations and steps played an important role in dislocation generation.

Y.Nabetani, A.Wakahara, A.Sasaki: Journal of Applied Physics, 1995, 78[11], 6461-8