Morphology and crystallography of CdS-CdTe double layers on various GaAs surfaces

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Abstract
Epitaxialdouble layers of CdS and CdTe have been grown on GaAs by close‐spaced chemical vapor transport, to study the growth of CdTe on various CdSsurfaces. Since the [00.1] axis of CdS aligns to one of the 〈111〉A axes of the GaAs substrate, the deposition of CdS on {111̄}A, {110}, and {100} GaAssurfaces yields approximately the {00.1}, {10.3}, and {11̄.1} CdSsurfaces. On {111̄}A and slightly inclined substrates the CdS‐CdTe layers (2–10 μm thick) grow uniformly thick with smooth surfaces. On the {110} and {100} faces the CdTe layers show a scale structure through the whole layer, which is approximately aligned to one of the 〈111〉 axes of the substrate. X‐ray investigations reveal three‐ and two‐dimensional lattice defects in the CdTe layer such as twinning, cubic‐hexagonal mixture, stacking faults, fiber texture, and polycrystallinity. The number of defects increases in layers grown on {111̄}A to {110} and to {100}. The most perfect layers on {111}A faces and slightly inclined ones have a cubic structure with twinning about the growth direction. On {110} and {100} faces, the [00.1] and [111̄] stacking axes of the three lattices are slightly tilted to each other. The tilt angle can be explained by an accommodation of the lattice mismatch at the interface in such a way that the stacking planes join together continuously at the boundaries.