Picosecond intersubband dynamics in p-Si/SiGe quantum-well emitter structures

We report time-resolved (ps) studies of the dynamics of intersubband transitions in P-Si/SiGe multiquantum-well structures in the far-infrared (FIR) regime, (h) over bar omega<<(h)over bar>omega(LO), utilizing the Dutch free electron laser, (entitled FELIX-free electron laser for infrared radiation). The calculated scattering rates for optic and acoustic phonon, and alloy scattering have been included in a rate equation model of the transient FIR intersubband absorption, and show excellent agreement with our degenerate pump-probe spectroscopy measurements where, after an initial rise time determined by the resolution of our measurement. we determine a decay time of similar to10 ps. This is found to be approximately constant in the temperature range from 4 to 100 K, in good agreement with the predictions of alloy scattering in the Si0.7Ge0.3 wells. (C) 2002 American Institute of Physics.