Electronic and optical properties of strained-layer superlattices made of semiconductor alloys

Abstract

We report theoretical calculations of the electronic and optical properties of strained-layer superlattices (SLS) made up of semiconductor alloys. The SLS conduction band states are obtained by using a two-band model capable of correctly describing the band structure over the entire Brillouin zone. This allows us to study intervalley scattering among the various conduction band valleys (Γ, L, X, etc.). Our model also allows us to easily incorporate the effects of strain on the band structure. Using this model we have studied materials such as Si/GeSi SLS, and the effects of zone folding and strain on the band structure and photoabsorption are reported. We have also studied the effect of disorder scattering in SLS made of alloy semiconductors by generalizing the coherent potential approximation (CPA) to the treatment of superlattices. The results are compared with those obtained within the virtual crystal approximation (VCA) which does not include disorder scattering.