A study was made of ZnS epilayers which had been grown onto (100)GaAs substrates by means of H transport vapor-phase epitaxy. The use of X-ray diffraction measurements, using both double-axis and single-axis modes, yielded the residual strain tensor and the strain versus temperature dependence of the epilayer at temperatures ranging from 25 to 650C. By analyzing the data which had been obtained by making double-axis measurements of several symmetrical Bragg reflections at various azimuth angles, and of asymmetrical reflections from various geometries, an orthorhombic distortion of the ZnS lattice was revealed. The crystallographic symmetry could be explained by an asymmetrical distribution of the misfit dislocation density, in the interface plane, along the [011] and [0¯11] directions. Temperature dependence measurements of the strain tensor components, at temperatures between ambient and 650C, permitted the determination of the misfit between ZnS and GaAs and of the linear thermal expansion coefficient of ZnS. Triple-crystal diffractometry and secondary-ion mass spectrometry were used to investigate the chemical nature of the ZnS/GaAs interface. The results revealed the presence of an interdiffused ZnS/GaAs interface region. Its existence was associated with the initial defect structure of the substrate surface before growth.

C.Giannini, T.Peluso, C.Gerardi, L.Tapfer, N.Lovergine, L.Vasanelli: Journal of Applied Physics, 1995, 77[6], 2429-34