Electronic parameters of the two-dimensional electron gas in modulation-doped single quantum wells due to an embedded deep step layer

Abstract

The Shubnikov–de Haas (S–dH) measurements at 1.5 K clearly demonstrated the existence of a two-dimensional electron gas (2DEG) in the modulation-doped Al0.25Ga0.75As/InyGa1−yAs/GaAs single and step quantum wells, and the fast Fourier transformation results for the S–dH data clearly indicated the electron occupation of one subband in the asymmetric single and step quantum wells. While the electron carrier density of the 2DEG in the step quantum well was larger than that in the single quantum well due to the larger conduction-band discontinuities, the mobility of the 2DEG in the step quantum well was smaller than that in the single quantum well because of the interface scattering resulting from the embedded step well. The electron effective mass in the step quantum well was smaller than that in the single quantum well, which was consistent with a smaller mass of the embedded deep step layer. The electronic subband energy, the energy wave function, and the Fermi energy in the InyGa1−yAs step quantum wells were calculated by using a self-consistent method taking into account exchange-correlation effects together with strain and nonparabolicity effects.