Choosing proper approximation for semiconductor device analytical modeling at low temperature

Abstract
The influence of nonlinear physical phenomena (namely electron-hole scattering, Auger recombination, reduction of the emitter junction efficiency) on the practicality of diffusive approximation in semiconductor multilayer device modeling is investigated. It is shown that there exists a certain sequence of proper approximations as the current density increases. An important point is that this sequence of approximations depends on the electrophysical parameters of the structure, namely on the ratio W/L (where W is the width of a lightly doped base layer of the structure, L is the ambipolar diffusion length of charge carriers in the base layer), the charge carrier lifetime τ and the saturation currents j_sn and j_sp of highly doped p₊ and n₊ layers. It is shown that at low temperature the dependence of saturation currents on electron-hole scattering becomes of importance. Owing to this the electron-hole scattering influences the validity of diffusive approximation as distinct from the case of high temperature