Carrier dynamics investigated by time-resolved optical spectroscopy

An optical investigation of the transport properties of carriers in a thick GaAs layer is presented. The electron transport is monitored by time-resolved luminescence from the GaAs layer and an InGaAs quantum well beneath. The transients are mostly insensitive to the presence of external electric fields of both polarities, which indicates a carrier transport dominated by ambipolar diffusion. Spin measurements under a continuous-wave low-density regime show a strong conservation of the electron spin during the diffusion of electrons through the thick GaAs layer and their capture by the InGaAs well, but only for an applied field polarity that accelerates the electrons towards the well.