Effect of lattice connectivity on the electronic structure of an amorphous semiconductor

HORACIO M. PASTAWSKI; LEOPOLDO DE BERNARDEZ; JUAN F. WEISZ

PHYSICAL REVIEW B - SOLID STATE

American Physical Society

Lugar: Ridge N.Y.; Año: 1985 vol. 32 p. 5468 - 5470

0556-2805

Phys. Rev. B 32, 5468 - 5470 (1985) Effect of lattice connectivity on the electronic structure of an amorphous semiconductor Within the structure of a-Si the addition of hydrogen can be thought to produce a decrease in the connectivity of the lattice, compared with the ideal fourfold-coordinated amorphous lattice. We simulate this effect with a Hamiltonian of the Weaire and Thorpe type, within which a proportion c of adjacent sp3 orbitals are eliminated. In this model the width of the gap is determined by the upper edge of the bonding p band and the lower edge of the sp antibonding band. We found that, as c increases the sp bands decrease in width while the pure p bands (the deltas in the Weaire and Thorpe model) do not modify their position. This causes an increase in the size of the gap which is in accordance with experimental observations for hydrogenated amorphous silicon. The results suggest that the effective dimension of the space where the carriers are constrained to move plays an important role in amorphous semiconductors.