Determination of the onset of plastic deformation in ZnSe layers grown on (100) GaAs by molecular-beam epitaxy

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Abstract
ZnSe layers were grown by molecular-beam epitaxy on (100) GaAs substrates to various layer thicknesses in the range 0.1–2.0 μm. The ZnSe lattice parameter normal to the heterointerface and the ZnSe and GaAs lattice parameters parallel to the heterointerface were measured by the single-crystal x-ray diffractometry technique using the high angle reflections obtained from the (006) and (444) planes. In addition, the heterointerfaces were examined by cross-sectional transmission electron microscopy. It was found that thin ZnSe layers (t<0.5 μm) grown on GaAs substrates are tetragonally distorted. The layers appear to be elastically strained up to a layer thickness in the range 0.15–0.2 μm whereupon a gradual strain-relief process occurs for layers in the thickness range 0.2≤t≤0.5 μm via the formation of misfit dislocations.