Strain relaxation in ZnSe/GaAs(001) heterostructure grown by molecular beam epitaxy is studied by transmission electron microscopy. In as-grown samples, an array of perfect misfit dislocations, lying along 310 directions, with Burgers vector (1/2) 011 inclined to the interface is observed. The corresponding threading segments propagate by glide in {331} planes, leaving misfit segments in the interface.From a mechanical equilibrium analysis, it is concluded that, in the case of low misfit (0.27%), the critical thickness for {331} planes is less than for {111} glide. Dislocations with the (1/2) 011 Burgers vector lying along 310 directions are more efficient at relaxing the misfit strain than dislocations lying along 110 directions.

A novel convergent-beam-electron-diOE raction method is discussed, which permits us to determine unambiguously the polarity of {001}-oriented semiconductor compounds with sphalerite structure. It is based on a comparison between experimental patterns and simulated patterns. At variance with {110}-oriented crystals, the polarity cannot be uniquely determined from observed intensity asymmetry in the {200} discs. Additional features have to be considered, such as the geometry and intensity of Kikuchi lines in the transmitted disc. Examples from ZnSe crystals are given.

ZnSe thin films grown on GaAs(001) substrate by molecular beam epitaxy to a thickness of 2500 Å have been studied by transmission electron microscopy (TEM). Three types of structural defect have been observed: (i) Triangle-shaped stacking faults, with the apex close to the interface, either isolated or paired. They are bounded by two different Shockley dislocations. (ii) Stacking faults generated from the surface of the ZnSe epilayer by movement of a Shockley half-loop. (iii) An array of perfect misfit dislocations. Their Burgers vectors are inclined to the interface. Most of them lie along ⟨310⟩ directions; only a few are parallel to ⟨110⟩.

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