Hot-electron conduction in Hg0.8Cd0.2Te in the extreme magnetic quantum limit at low temperatures

Abstract

A theoretical analysis of hot-electron transport in narrow-gap semiconductors under a large magnetic field is developed at low temperatures. The energy relaxation time and the electric-field dependence of the drift velocity of hot electrons in Hg0.8Cd0.2Te at 1.5 K in the extreme quantum limit, i.e., when all the electrons occupy the lowest Landau subband, are calculated. The model includes scattering by the acoustic phonons and other complexities such as the band nonparabolicity, free-carrier screening, nonequipartition of phonons, and the level broadening due to electron-impurity interactions. The theoretical results are compared with the experimental data on the energy relaxation time in Hg0.8Cd0.2Te for magnetic flux densities of 4 and 6 T. When the equilibrium phonon distribution is considered, the theoretical values are found to be several times less than the experimental values. The discrepancy is attributed to the nonequilibrium phonons or ‘‘hot phonons’’ that exist under hot-electron conditions. Including the hot-phonon effects, the theoretical results are in satisfactory agreement with the experimental data, giving a reasonable estimate of the phonon life time. The model has been applied to calculate the electric field dependence of the drift velocity of hot electrons in Hg0.8Cd0.2Te at 1.5 K in the extreme quantum limit by assuming scattering by the nonequilibrium acoustic phonons and ionized impurities, and a satisfactory agreement with the experimental results is obtained.