Microtwinning in stress-relaxed In1 –xGaxAs/(001) InP hetero-epitaxial layers

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Abstract
Electron micrographs and selected area diffraction patterns of single In 1 – x Ga x As epitaxial layers (cubic symmetry, space group F [unk]3 m ) have been studied using transmission through the specimen edges formed by intersection of the (001) growth surface and the (0[unk]), (1[unk]0) or ([unk]0) cleavage faces. For (001)/(0[unk]) edge transmission lamellae (thickness between 7 and 21 nm) of deformation twins parallel to ([unk]1) were detected unambiguously. Micron-deep grooves are formed where twins intersect the (001) surface. Twin growth proceeds by propagation of Shockley partial dislocations from a surface-near region towards the layer/substrate interface, leaving a sessile dislocation behind. A possible mechanism of twin growth is discussed on the basis of a repeated dissociation of such sessile dislocations into glissile Shockley partials.