Dependence of the electronic parameters on the InyGa1−yAs quantum well width in modulation-doped AlxGa1−xAs/InyGa1−yAs/GaAs strained single quantum wells

The variation of the electronic parameters in the subband as a function of the InyGa1−yAs quantum well width in modulation-doped strained AlxGa1−xAs/InyGa1−yAs/GaAs single quantum wells were investigated by means of Shubnikov-de Haas (S-dH) and Van der Pauw Hall-effect measurements. The fast Fourier transform (FFT) of the S-dH oscillations and the Hall-effect data showed that the carrier density and the mobility of the two-dimensional electron gas (2DEG) occupied in the subband increased as the quantum well width increased. The increase in the 2DEG density with increasing the InyGa1−yAs well width originated from an increase in the energy difference between the energy level of the electronic subband and Fermi energy, and the increase in the 2DEG mobility is attributed to a decrease of the scattering source. The electronic subband energies, the corresponding wavefunctions, and the Fermi energies in the AlxGa1−xAs/InyGa1−yAs/GaAs single quantum wells were calculated by a self-consistent method taking into account the exchange-correlation effect together with the strain and nonparabolicity effects. These results indicate that the electronic parameters in AlxGa1−xAs/InyGa1−yAs/GaAs strained single quantum wells are significantly dependent on the quantum well width.