Modeling of electron energy spectra and mobilities in semi-metallic Hg_1−xCd_xTe quantum wells

Electron mobility, energy spectra, and intrinsic carrier concentrations in the n-type Hg_0.32Cd_0.68Te/Hg_1−xCd_xTe/Hg_0.32Cd_0.68Te quantum well (QW) in semi-metallic state are numerically modeled. Energy spectra and wave functions were calculated in the framework of the 8-band k-p Hamiltonian. In our model, electron scattering on longitudinal optical phonons, charged impurities, and holes has been taken into account, and the mobility has been calculated by an iterative solution of the Boltzmann transport equation. Our results show that the increase of the electron concentration in the well enhances the screening of the 2D electron gas, decreases the hole concentration, and can ultimately lead to a high electron mobility at liquid nitrogen temperatures. The increase of the electron concentration in the QW could be achieved in situ by delta-doping of barriers or by applying the top-gate potential. Our modeling has shown that for low molar composition x the concentration of holes in the well is high in a wide range of electron concentrations; in this case, the purity of samples does not significantly influence the electron mobility. These results are important in the context of establishing optimal parameters for the fabrication of high-mobility Hg_1−xCd_xTe quantum wells able to operate at liquid nitrogen temperature and thus suitable for applications in terahertz detectors