  Electron mobility, energy spectra and intrinsic carrier concentrations in the
n-type Hg0.32Cd0.68Te / Hg1-xCdxTe / Hg0.32Cd0.68Te 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 Hg1-xCdxTe quantum wells able to operate at liquid
nitrogen temperature and thus suitable for applications in terahertz detectors.
