Intersubband quantum cascades in the Si/SiGe material system

Abstract

Si/SiGe quantum cascade structure of 3×4 periods show well-resolved intersubband electroluminescence, whose nonradiative lifetimes are found to depend strongly on the design of the quantum well structure, and are shown to reach values comparable to that of an equivalent GaInAs/AlInAs laser structure. Problems that need to be overcome for the realization of a Si/SiGe quantum cascade laser are discussed in relation to structures on relaxed SiGe buffer layers. Initial experiments using Si0.2Ge0.8/Si on Si0.5Ge0.5 buffer layers show well-resolved intersubband absorption between two heavy hole states in the quantum wells.