Effects of Pressure on the Electronic and Optical Properties of a Polymorph of Germanium and of Amorphous Germanium

It has been observed experimentally that the density dependence of the energy gap of a tetrahedrally coordinated amorphous semiconductor is generally smaller than that of its crystalline form. Using the Ge 3 or ST12 structure as a simple model of amorphous Ge (a-Ge), the electronic structure of this simple model of a-Ge, calculated using the pseudopotential method, is obtained at several densities. The resulting density dependence is found to be small.