Short-Range Order and Pseudogaps in Elemental Amorphous Covalent Semiconductors

Abstract

The role of short-range order in producing a pseudogap in the density of states $\rho \mathrm{}\left(E\right)\mathrm{}$ of an elemental amorphous material is investigated. An approximate expression for $\rho \mathrm{}\left(E\right)\mathrm{}$ which emphasizes short-range order and neglects all long-range order is derived from multiple-scattering theory. This expression is used to study the influence of short-range order consisting of two atoms, a single bond, and eight atoms in the staggered and eclipsed bonding configurations on $\rho \mathrm{}\left(E\right)\mathrm{}$. The results of numerical calculation for amorphous $s{p}^3$-bonded C, amorphous Si, and amorphous Ge are reported. These results suggest that the pseudogap in $\rho \mathrm{}\left(E\right)\mathrm{}$ may be attributed to the short-range order.