A new study of critical layer thickness, stability and strain relaxation in pseudomorphic gexsi1-xstrained epilayers

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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 hc becomes invalid. A method to calculate the correct critical layer thickness hci' taking into account the interactions, is given. Values of hci are always smaller than hc but the difference hc—hci is small. The concentration of dislocations present in thick epilayers (i.e. with hhci) 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.