A new study of critical layer thickness, stability and strain relaxation in pseudomorphic ge_xsi_1-x strained epilayers

Abstract

The predicted energy of an array of dislocations in semiconductor epilayers is considerably reduced due to interactions between the dislocations. It is found that when the effects of interactions are taken into account, the existing expression for critical layer thickness h_c becomes invalid. A method to calculate the correct critical layer thickness h_ci' taking into account the interactions, is given. Values of h_ci are always smaller than h_c but the difference h_c—h_ci is small. The concentration of dislocations present in thick epilayers (i.e. with hh_ci) in stable equilibrium increases considerably due to interactions. The rates of plastic flow and strain relaxation on annealing the metastable epilayers also increase. The values of phenomenological constants present in the plastic flow theories which are used to interpret experiments are much reduced when interactions are properly taken into account.