ABSTRACT
A theory that makes an explicit connection between scattering-limited ohmic mobility and quantum-emission-limited saturation velocity is presented. The theory is applied to electrons in bulk silicon by taking a quantum equal to the energy of an optical phonon. Because this quantum emission is indicated, a modication in the mfp appears only in the high-eld regime. This modication is shown to lead to electric-eld-induced degradation of the diffusion coefcient. The theory presented agrees with the drift-diffusion experimental data and empirical relations utilized in modeling devices. The theory makes connections with an alternate description in terms of electron temperature under ac and dc conditions. As drift-diffusion processes are central in the performance evaluation of submicron-scale devices where high elds are necessarily present, these results contribute signicantly in reshaping thinking processes in the high-eld regime. Transfer to higher valleys in multivalley band structure is also discussed.
