Electronic subband studies in In0.52Al0.48As/In<i>x</i>Ga1−<i>x</i>As one-side-modulation-doped asymmetric coupled double quantum wells

Abstract

Shubnikov–de Haas (SdH) and van der Pauw Hall effect measurements on In0.52Al0.48As/InxGa1−xAs coupled double quantum wells grown by metalorganic chemical vapor deposition have been carried out to investigate the magnetotransport properties of an electron gas and to determine the subband energies and wave functions in the coupled quantum wells. Transmission electron microscopy measurements showed that In0.8Ga0.2As and In0.53Ga0.47As quantum wells were separated by an In0.25Ga0.75As potential barrier in an active region. The SdH measurements at 1.5 K demonstrated clearly the existence of a quasi-two-dimensional electron gas in the quantum wells. The fast Fourier transformation results for the SdH data clearly indicate the occupation of three subbands in the In0.52Al0.48As/InxGa1−xAs coupled quantum wells. Electron subband energies and wave functions in the quantum wells were calculated by a self-consistent method taking into account exchange-correlation effects. The first and second excited subband wave functions in the asymmetric quantum well are strongly coupled over both In0.8Ga0.2As and In0.53Ga0.47As wells.