Interface-roughness-induced broadening of intersubband electroluminescence in p-SiGe and n-GaInAs/AlInAs quantum-cascade structures

Abstract

The effect of intrasubband interface roughness scattering on intersubband transition linewidths in double-quantum-well and quantum-cascade (QC) structures is studied. In n -GaInAsAlInAs structures, the calculated ratios between the linewidths of the spatially vertical and diagonal transitions agree with the experimental values. In p -Si Si0.2Ge0.8 QC structures, the experimentally observed linewidth is a factor of 4-7 smaller than the predicted value. However, by assuming a vertical interface correlation between adjacent interfaces separated by less than ~1.5 nm, the theory reproduces the experiment. Transmission electron microscopy of the SiGe QC sample reveals this vertical correlation, supporting the model.