Optical spectra and recombination in SiGe/Si heterostructures for infrared applications

We report a study of absorption and Auger recombination in p-type SiGe/Si heterostructures in which the Ge concentration has been varied from 15% to 50%, with a view to assessing the optimum condition for infrared applications in the 3–5 and 8–15 μm ranges. Our results have been obtained by full scale microscopic calculations in which the effects of the crystal potential, doping and well width upon the strength and frequency of the absorption response have been considered. We present a detailed comparison of our theoretical optical lineshapes with those obtained in recent experiments for both parallel and normal incident light. Finally, we identify the band structure properties that are necessary for the reduction of Auger recombination in systems of practical importance and present preliminary results for the Auger rates in these structures.