Hot-electron galvanomagnetic coefficients of polar semiconductors

Hot-electron galvanomagnetic effects in polar semiconductors (III-V and mixed) are studied considering the effects of different phonon scattering mechanisms. The effect of interelectronic collisions is taken into account by considering three different carrier concentrations - high, medium and low. In the high-concentration case a displaced Maxwellian distribution of carriers with a field-dependent effective temperature makes the ratio of Hall and conductivity mobilities equal to unity and the magnetoresistance coefficient zero, independent of electric and magnetic fields (for single-valley semiconductors only). In the medium- and low-carrier-concentration cases, on the other hand, the Hall mobility and magnetoresistance coefficient are highly dependent on the fields. Methods for calculation in two-valley semiconductors (GaAs, InP, etc.) are also discussed. Numerical results have been presented for acoustic and polar-optical phonon scattering and single-valley semiconductors with isotropic effective mass in the medium-concentration case. It is found that for the case of polar-optical scattering the magnetoresistance coefficient varies by several orders of magnitude for changes in the magnetic field. The dielectric breakdown field is also found to depend slightly on the magnetic field. The effect of these results on some recent experiments is discussed.