Strain compensated Si/SiGe quantum well and quantum cascade on Si 0.5Ge 0.5 pseudosubstrate

Abstract

This study follows up our previous investigation of the valence band (VB) intersubband emission from quantum cascade structures grown lattice matched on Si substrates. Here, Si/Si 1−x Ge x (x=80%) heterostructures are investigated which are deposited by MBE on a virtual substrate of relaxed SiGe containing 50% of Ge. TEM analysis reveal flat and abrupt interfaces for structures grown at temperatures T growth≈300°C. Intersubband absorption and photoluminescence emission manifest well-defined interfaces and good material quality. The observed intersubband line positions are found to be in good agreement with k· p model calculations for the VB. This is in contrast to the observed type II no phonons recombination which is found at consistently lower energy than expected. Finally, electrically excited intersubband emission from a strain compensated cascade structure containing three periods is presented.