Impact ionisation threshold energy surfaces for anisotropic band structures in semiconductors

Abstract

A method has been developed for computing the impact ionisation threshold surface for anisotropic energy band structures in semiconductors. This has been applied to the anisotropic, nonparabolic band structure given by the k.p method, the parameters for which ar determined by fitting to the band structure of accurate pseudopotential calculations. This provides a realistic band structure which is consistent with the wavefunctions and hence the overlap functions used in transition rate calculations. Application is made to the CCCH (electron-electron) transition and the CHLH (light-hole-heavy-hole) transition in InSb, InAs, InP, GaAs and GaSb. The noncollinearity of the wavevectors at threshold for these anisotropic band structures is also examined.