Long-Range Order and Segregation in Semiconductor Superlattices

Abstract

Results of self-consistent energy-minimization calculations provide strong evidence that the ordered phases in epitaxially grown ${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ and strained ${\mathrm{Si}}_{1-x}{\mathrm{Ge}}_x$ alloys are metastable, in the sense that segregation into constituents is favored. We show that the long-range order in intermediate metastable structures leads to significant changes in the electronic properties of semiconductor superlattices. Segregation gives rise to micro-quantum-wells with staggered band lineup and multiple confined states in the potential barrier.