Magnetotransport, magneto-optical, and electronic subband studies in In_xGa_1-xAs/In_0.52Al_0.48As one-side-modulation-doped asymmetric step quantum wells

Shubnikov-de Haas (SdH), Van der Pauw Hall-effect, and cyclotron resonance measurements on In_xGa_1-xAs/In_0.52Al_0.48As asymmetric step quantum wells were carried out to investigate the electrical properties of a free electron gas and to determine the effective mass of the electron gas, the subband energies, and the wave functions in the In_xGa_1-xAs quantum wells. The SdH measurements at 1.5 K demonstrated clearly the existence of a quasi-two-dimensional electron gas in the In_xGa_1-xAs quantum wells, and the fast Fourier transformation results for the SdH data indicated clearly the occupation by that gas of two subbands in the quantum wells. The electronic effective masses determined from the slopes of the main peak absorption energies as a function of the magnetic field were 0.0477 and 0.053 m_e for the first excited and the ground subbands, respectively. The electronic subband energies and the wave functions in the In_xGa_1-xAs/ In_0.52Al_0.48As step quantum wells were calculated by a self-consistent method taking into account exchange-correlation effects together with the strain and nonparabolicity effects. The results of the cyclotron resonance measurements qualitatively satisfied the nonparabolicity effects of the step quantum well. These results can help improve understanding for the application of In_xGa_1-xAs/In_0.52Al_0.48As step quantum wells in optoelectronic devices.