EFFECT OF THE LOCAL DISORDER IN A-SI ON THE ELECTRONIC DENSITY OF STATES NEAR THE BAND EDGES

We have systematically investigated the formation of electronic states in the region of the conduction and valence band edges of a-Si as functions of variations in the bond and dihedral angle distributions. Local Densities of States (LDOS) for Si atoms in disordered environments have been calculated using the cluster Bethe lattice method with a Hamiltonian containing both first and second nearest neighbor interaction terms. We conclude that the changes in orbital overlap, incurred from rotations about the axes defining the dihedral angle distortions, are the origin of the effect of dihedral angle disorder on the electronic states near the band gap.