Determination of the deformation state of HgSe / ZnTe layers

High-resolution X-ray diffraction is commonly used to measure the misfit strain and to determine the unstrained lattice parameter of epitaxial semiconductor layers assuming tetragonal distortion. A method is developed which links the measured inter-planar spacings to the deformation tensor without assumption of layer symmetry. For the system HgSe on a thick ZnTe buffer layer deposited by MBE on GaAs substrate, the six components of the reciprocal metric tensor of each layer are determined by a least-squares algorithm from a set of reciprocal lattice vectors (137, 553). A principal-axis transformation of the calculated deformation tensor shows that the deformation nearly parallel to the [110[ and [110[ directions in the interface plane differs by more than 15 %. This difference is a function of the epilayer thickness and reaches a maximum for layers slightly thicker than the critical thickness