ELECTRONIC LIFETIMES IN EXCITED-STATE LANDAU-LEVELS

We have determined for the first time the inter-Landau level lifetimes in GaAs/GaAlAs heterostructures in the spin polarized region (filling factor < 1). Intensity-dependent cyclotron resonance absorption has b een measured using a high-intensity optically pumped far-infrared (FIR ) laser. A detailed analysis of the lineshape of the cyclotron resonan ce absorption within a Drude model shows saturation at intensities of 0.1 W cm-2. The electronic lifetimes deduced using a three-level model depend inversely on the electron concentration in the excited Landau level, indicating electron-electron scattering to be the dominant rela xation mechanism.