Effect of the non-equivalent intervalley scattering on the high-field conductivity characteristics of n-Ge

Abstract

Room-temperature velocity-field characteristics of n-type germanium have been calculated taking into account the effect of non-equivalent intervalley scattering in addition to that of intravalley acoustic, optical and equivalent intervalley phonon scattering. The analysis has been made on the assumption of a field-dependent displaced Maxwellian distribution function for the electrons in the <111> valleys and field-independent mobility for the electrons in the <100> valleys. The calculated values are found to agree with the results of Monte Carlo calculations to within 10 per cent. It is also found that the calculated characteristic agrees with experiments very closely if the values of the deformation potential constant for the intravalley optical phonon scattering and for the nonequivalent intervalley scattering are taken to be 0.5×10⁹ and 0.5×10⁸ eV cm^-1, respectively. The non-equivalent intervalley scattering introduces saturation in the velocity-field characteristics and at the same time reduces the temperature of the electrons in the <111> valleys sufficiently to eliminate the possibility of breakdown.