N-TYPE SIGE HETEROSTRUCTURES FOR THZ INTERSUBBAND TRANSITIONS

Research on band-gap engineering of Silicon-Germanium heterostructures for the realization of Quantum Cascade (QC) structures emitting in the Terahertz (THz) spectral region has recently attracted a vast interest. While several successful attempts have been reported using hole-based (p-type) intersubband transitions, very few results have been published on systems exploiting electrons (n-type). In this work we present the optical and structural characterization of n-type heterostructures made either of tensely-strained Si (sSi) quantum well (QW) confined between low Ge content Si1-xGex barriers [0.2<x<0.5] or of compressively-strained Ge (sGe) QW confined between high Ge content Si1-xGex barriers [0.8<x