Magnetotransport studies of the two-dimensional electron gas in modulation-doped Al xGa 1− xAs/In yGa 1− yAs/GaAs asymmetric step quantum wells

Abstract

Low-temperature electrical transport properties of the two-dimensional electron gas (2DEG) in modulation-doped Al 0.25Ga 0.75As/In 0.18Ga 0.82As/In 0.25Ga 0.75As/GaAs asymmetric step quantum wells were studied by Shubnikov–de Haas (S–dH) and Van der Pauw Hall-effect measurements. The angular dependent S–dH measurements at 1.5 K demonstrated clearly the existence of a quasi-2DEG in the In x Ga 1− x As step quantum wells, and the fast Fourier transformation results for the S–dH data clearly indicate the electron occupation of one subband in the Al 0.25Ga 0.75As/In 0.18Ga 0.82As/In 0.25Ga 0.75As/GaAs asymmetric step quantum wells. The electron carrier density and the effective mass determined from the S–dH measurements were 1.76×10 12 cm −2 and 0.06603 m 0, respectively. The electronic subband energy, the energy wavefunction, and the Fermi energy in the In x Ga 1− x As step quantum wells were calculated by a self-consistent method taking into account exchange-correlation effects together with the strain and nonparabolicity effects. These present results can help improve understanding for the potential applications of modulation-doped Al 0.25Ga 0.75As/In 0.18Ga 0.82As/In 0.25Ga 0.75As/GaAs asymmetric step quantum wells in new kinds of the high-speed electronic devices.