MODEL-CALCULATIONS OF OPTICAL-PROPERTIES FOR DISORDERED GAAS/ALAS SUPERLATTICES

We have investigated the role of disorder in effecting the optical properties of short period superlattices. A one-dimensional, two atoms per unit cell, tight binding model of a superlattice is solved exactly for the ordered structure and for a given disorder in the growth direction. A difference vector and the resulting disorder structure factor are proposed to characterize the disorder. The density of states, participation number, and optical absorption for both the ordered and disordered superlattice models are calculated as a function of energy. The results show that introduction of disorder into an indirect band gap material enhances the optical transitions near the indirect band edge.