Determination of residual strain by reflectivity, X-ray diffraction and Raman spectroscopy in ZnSe epilayers grown on GaAs (001), InP(001) and GaSb(001) by metal-organic vapor phase epitaxy

Abstract

Reflectivity, X-ray diffraction and Raman spectroscopy allowed determination of the residual strain in ZnSe epilayers grown on different substrates such as GaAs(001), InP(001) and GaSb(001) by metal-organic vapor phase epitaxy. The lattice mismatch as well as the difference in thermal expansion coefficients induced a residual strain in the layer. In ZnSe/GaAs(001) heterostructures both compressive and tensile strains were observed owing to the lattice mismatch (0.27%) and to the difference in thermal expansion coefficients between the layer and the substrate. ZnSe epilayers grown on InP(001) (lattice mismatch −3.5%) and grown on GaSb(001) (lattice mismatch −7%) are under tensile strain owing to the difference in thermal expansion coefficients. A relaxation on thermal strain is observed in both cases when the layer thickness is increased from 0.2 to 2 μm (ZnSe/InP) and from 1 t0 7 μm (ZnSe/GaSb). In spite of the difference in measurement temperature and also in the thickness range analyzed by reflectivity, X-ray diffraction and Raman spectroscopy, the strain determined using these methods is of the same order of magnitude.