MECHANISM FOR CUPT-TYPE ORDERING IN MIXED III-V EPITAXIAL LAYERS

A model is proposed to rationalize the occurrence of CuPt-type ordering in mixed III-V epitaxial layers grown on (001) substrates. It is invoked that 2 X surface reconstruction occurring on group V terminated (001) surfaces produces dilated and compressed regions in sub-surface layers. The presence of these regions biases the occupation of certain sites during the growth of a layer consisting of atoms differing in their tetrahedral radii. By assuming that the reconstruction always occurs at the growing surface, it is possible to explain the evolution of CuPt-type ordering in epitaxial layers. Also, based on the model, experimental observations pertaining to the influence of growth conditions, surface misorientation and steps on ordering can be rationalized.