Role of recombination and impact ionization in intervalley repopulation effects

It is shown that electron recombination and impact ionization with donors give contribution to the intervalley scattering (IS) in many-valley semiconductors. The IS probability (ISP) due to recombination coincides with the phenomenological ISP which was previously introduced to explain experimental results. The electron concentration n increases monotonically, when the electric field E increases, and it is practically independent of the orientation of E relative to crystallographic axes in the range of E<E_c, where recombination gives the main contribution to the ISP. n strongly depends on the orientation of E for E#62;E_c and the dependence of n on E may be even N-shape due to strong intervalley repopulation.