Model of hydrogenated amorphous silicon and its electronic structure

Using previously generated large models of pure amorphous silicon [J. M. Holender and G. J. Morgan, J. Phys. Condens. Matter 3, 7241 (1991)] we have now constructed structural models of hydrogenated silicon. They are obtained by ``hydrogenation'' of our models of amorphous silicon, i.e., by addition of the hydrogen atoms into a model of a-Si containing undercoordinated and overcoordinated atoms followed by relaxation using molecular dynamics. The electronic structure of the models is calculated using the phenomenological tight-binding model. It is shown that addition of hydrogen reduces drastically the density of electronic states associated with defects, producing a clearly defined gap.