Optical absorption spectroscopy of Si-Ge alloys and superlattices.

Abstract

We report calculations and measurements of the optical absorption coefficient of SinGe m superlattices and alloys where n’m. Our results can be used to determine the fundamental band gap, the dependence of the band gap on superlattice period, and the absorption coefficient near the band-gap energy. Both theory and experiment show that all short-period ( n1m,20) superlattices display a similar linear dependence of absorption coefficient on photon energy. This behavior is different from alloys of the same average composition where we measure that the absorption coefficient increases with the 3 power of photon energy. @S0163-1829~96!02627-6#