Intersubband transitions in n-type group IV quantum cascade lasers

In a theoretical investigation of intersubband transport in SiGe based quantum cascade structures, we show that low effective mass and a large confining potential may be achieved with either (001) oriented Ge-rich or (111) orientated Si-rich structures. Using a self-consistent time-independent perturbation/rate equation approach, we predict net gain in both systems and compare their maximum operating temperatures.