Large and small angle x-ray scattering studies of CdTe/MgTe superlattices

We have performed large and small angle x-ray scattering measurements on Cd Te/MgTe superlattices. The individual thicknesses of the CdTe and MgTe laye rs, together with the period dispersion and the crystallographic quality of the stacking, were extracted from large-angle x-ray diffraction. The Fresn el optical method and the distorted wave Born approximation were used to an alyze the small angle x-ray scattering data. Specular reflectivity shows th at the interface roughness is quite large for the two CdTe/MgTe superlattic es grown either by conventional molecular beam epitaxy or by atomic layer e pitaxy with however in the latter case a strong asymmetry between the direc t and inverted interfaces. The effective MgTe concentration is determined f rom the refractive index. A model of correlated interface profiles is succe ssfully used to simulate the diffuse scattering, and to gain access to the lateral correlation length of the roughness (Lambda(parallel to) = 1500 +/- 750 Angstrom for both samples); moreover, we demonstrate that the layers a re almost completely correlated over the sample thickness in the growth dir ection. (C) 1999 American Institute of Physics. [S0021-8979(99)06216-7].