Abstract
The cluster-Bethe-lattice method and a simple model Hamiltonian have been used to determine the influence of short-range order on the valence band and direct optical gap of Ge-Si alloys. The results predict that an ionic gap occurs for only a very narrow range of concentration and correlation, and that the deviation from linearity of the direct optical gap decreases as the probability of Ge-Si bond increases. A possible method of deriving the degree of short-range order from photoemission studies is suggested.
Keywords