CRITICAL THICKNESS IN HETEROEPITAXIAL GROWTH OF ZINCBLENDE SEMICONDUCTOR COMPOUNDS

It is assumed that the critical layer thicknesses (CLT) in strained heteroepitaxial layers of zinc-blende semiconductor compounds depend on an energy balance relation between the strain energy and the deformation energy induced by the misfit dislocations. The first energy is evaluated by theoretical means and confirmed by calculation. In order to calculate the latter energy, we have developed an interfacial misfit dislocation model in association with a computer simulation method based on Keating's valence force field approximation. In this way the energy of the relaxed grown layer is obtained in the case of a complete network of two-dimensional misfit dislocations. The computer simulation results are compared with published experimental data. The predicted values are in excellent agreement with the experimental CLT measurements for CdTe on CdZnTe substrates as well as for GeSi on Si substrates, over the entire alloy compositional range. It is shown that the CLT depends in fact only on lattice mismatch eta. The eta-3/2 law of variation of the CLT found in this way may thus be considered as quite general and is extended to GaInAs/GaAs, GaSbAs/GaAs and GaInAs/InP systems.