TRANSPORT-EQUATIONS IN INHOMOGENEOUS SEMICONDUCTORS

A generalized equation for the transport of a physical quantity in inhomogeneous semiconductors is derived from the Boltzmann transport equation. The momentum and energy transport equations, obtained from this equation, extend the previous equations of Blotekjaer and Azoff to inhomogeneous semiconductors with nonparabolic band structure. The momentum transport equation is used to derive a steady state electric current density equation in the relaxation time approximation of the Boltzmann transport equation. It provides an alternative form of the electric current density equation, obtained earlier by the present author. The electric current density is expressed in terms of a generalized drift and various generalized diffusion terms. Explicit expressions of diffusion coefficients are obtained by making plausible approximations which, for the low electric field, gives the results of the first order theory of the Boltzmann transport equation.