Dislocation densities in MBE grown ZnSe epitaxial layers on GaAs by HRXRD

In this work, we report on dislocation densities in MBE grown ZnSe/GaAs/GaA s heterostructures of different epilayer thickness. We examined the full-wi dth at half-maximum of the reflection peaks obtained by high-resolution X-r ay diffraction. We observed three regimes of dislocation generation. The fi rst regime is present for samples of subcritical thickness, where only stac king faults are present and their formation depends on the conditions of pr eparation of the substrate and the initial conditions of growth. The second regime exists for samples with layer thickness greater than the critical t hickness and thinner than a threshold thickness ht congruent to 0.3 mu m, w here a large amount of misfit and threading dislocations are generated. The third regime starts for layer thickness greater than h(t). In this regime the formation of dislocations is substantially slowed down and the dislocat ion density follows a 1/h dependence as predicted by the glide model. Compa ring dislocation densities obtained by X-ray diffractometry with the pit de nsity revealed by chemical etching of one sample and those observed by tran smission electron microscopy of two samples, agreement exists among them wi thin the same order of magnitude. (C) 1998 Elsevier Science B.V. All rights reserved.