Quantum and transport mobilities in an AlGaAs∕GaAs parabolic quantum-well structure

We study quantum and transport mobilities in a parabolic quantum-well structure when one or more subbands are occupied. We developed an original analytical method to extract the quantum mobility from the multiple occupied subband transport characteristics at low temperature. We tune the carrier density and hence the subband structure of the parabolic quantum well over a wide range by illumination with a red light-emitting diode. In order to obtain the quantum mobilities, Fourier transforms of the first differential of the experimental magnetoresistance traces (ρxx versus magnetic field) are taken and fitted by a conductivity tensor model in the same magnetic field range. We find that both the quantum and transport mobilities increase nonlinearly with increasing carrier density for both the first and second subbands and conclude that the intersubband scattering is predominantly large angle.