Control and probe of carrier and spin relaxations in InSb based quantum wells

The growing interest in spin-related phenomena and devices has prompted intense activity in the science and engineering of narrow gap semiconductors (NGS). NGS offer several scientifically unique features such as small effective masses, large g-factors, high intrinsic mobilities, and large spin- orbit coupling effects. In this work we report the dynamics of photo-excited carrier/spin in several InSb based quantum wells (QWs) using standard pump-probe spectroscopy and magneto- optical Kerr (MOKE) effect. Our InSb QWs are grown on GaAs (001) substrates with the Al$_{x}$In$_{1-x}$Sb barrier layers. We studied one undoped and five doped QWs with the electron concentrations in the wells ranging from ${\sim}1-4.4{\times}10^ {11}cm^{-2}$, where only the ground-state subband is occupied. The electron mobility in the samples are ranging from ${\sim} 70,000-100,000 cm^{2}/Vs$ at 4.2 K. We observed strong dependence of the dynamics to the density of photo-excited carriers and the pump photon energy and only weak variation with changing the samples' temperature. Our results are important to understand different relaxation mechanisms in NGS with strong-spin orbit interactions.