Picosecond Time-Resolved Cyclotron Resonance Study of Intra- and Inter-Landau Level Relaxation in InSb Quantum Wells

We have measured the picosecond time-resolved cyclotron resonance(J. Kono et al., Appl. Phys. Lett. 75), 1119 (1999). of photo-generated transient carriers in InSb quantum wells by two-color pump-probe spectroscopy in a magnetic field. The sample was grown by MBE and contained 25 periods of 35 nm InSb well separated by 50 nm of Al_0.09In_0.91Sb barrier. The strong conduction band nonparabolicity of InSb causes the average cyclotron mass of the electrons, which we monitor directly in time, to decrease as the electrons relax towards the band edge. In addition, the nonparabolicity results in multiple cyclotron resonance lines due to the strongly energy dependent mass and g-factor, allowing us to carry out a detailed study of spin-flip and spin-conserving relaxation in the time domain. We gratefully acknowledge support from NSF DMR-9970962, DMR-9973167, DMR-0080054, DMR-0134058 (CAREER), DARPA MDA972-00-1-0034, ONR N00014-94-1-1024, JST and NEDO.