THEORETICAL APPROACH TO THE ELECTRONIC-STRUCTURE OF TETRAHEDRALLY-BONDED AMORPHOUS SOLIDS

On the basis of a simple method by which quantitative disorder as well as topological disorder in amorphous solids can be treated systematically, we study the electronic density of states of tetrahedrally-bonded amorphous semiconductors such as amorphous silicon or germanium. We adopt the Weaire-Thorpe model and apply the coherent potential approximation to the random variations of the banding parameter V1 and the bonding parameter V2 of this model. It is possible to explain the disappearance of the dip between the two lower peaks of the valence band by introducing fluctuations in V1 alone. This fact indicates that it is not always necessary to assume the existence of five-membered rings as a cause for the disappearance of the dip. We also discuss the effects of fluctuations in V2, missing atoms and broken bonds. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.