A MECHANISM OF MISFIT DISLOCATION REACTION FOR GAINAS STRAINED LAYERS GROWN ONTO OFF-AXIS GAAS SUBSTRATES

The structure of misfit dislocations at the interface between compressively strained epitaxial In0.12Ga0.88As and GaAs had been studied by TEM. Two dislocation line directions, separated by approximately 2-degrees in both the nominal [110] and [110BAR] directions, are observed for growth on (001) substrates tilted approximately 2-degrees off toward (010). Only [110] and [110BAR] glide directions are observed for growth on nominally on-axis substrates. It is shown that the misfit dislocations are constrained to lie in the interface plane often generating long segments of edge dislocation where the misfit dislocations are forced to converge by the low angle offset. The edge segments curve out of the interface plane into the buffer layer.