Electronic consequences of ideal local order in amorphous Si

We identify polytope models of tetrahedrally bonded amorphous semiconductors with the ideal covalently bonded Si regions of a-Si. For these regions we calculate the optical absorption spectrum and find a relatively weak absorption edge. Disorder-enhanced absorption is a result of localized states. Within the context of a quantum well model the energy dependent optical matrix element is related to well size. © 1983.