SATURATION SPECTROSCOPY AND ELECTRONIC-STATE LIFETIMES IN A MAGNETIC-FIELD IN INAS ALXGA1-XSB SINGLE QUANTUM-WELLS/

Saturation spectroscopy of electronic states in InAs/AlxGa1-xSb single -quantum-well structures has been carried out with the UCSB free-elect ron laser. An effective Landau-level lifetime is extracted from the cy clotron-resonance (CR) saturation results on a semiconducting sample ( x = 0.5) with the help of an n-level rate equation model. The effectiv e lifetime shows strong oscillations (greater than an order of magnitu de) with laser frequency with minima shifted to higher frequencies tha n given by the simple parabolic magnetophonon resonance condition due to large nonparabolicity in the InAs conduction band. Similar saturati on studies of two lines (the X line and CR) in a ''semimetallic'' samp le (x= 0.1) show markedly different effective lifetimes, demonstrating that the two lines are of different origin.