Modeling the structure of amorphous tetrahedrally coordinated semiconductors. I

Abstract

A continuous random network (CRN) consisting of 238 tetrahedrally coordinated atoms has been constructed so as to contain only even-membered rings. The structural properties of the model (density, bond-length distribution, bond-angle distribution, dihedral-angle distribution, radial distribution function) are in satisfactory agreement with experimental results for amorphous Ge, Si, and the III-V compounds. The present model eliminates the conflict between the Polk CRN model, which contains approximately 50% of odd-membered rings, and experimental photoemission, optical, and heat-of-crystallization results for the amorphous III-V's, which indicate the absence of a significant number of such rings. Comparison of the CRN models suggests that a determination of the experimental dihedral-angle distribution of each material is very important for a unique definition of its structure.