Effect of high injection level phenomena on the feasibility of diffusive approximation in semiconductor device modeling

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 the lightly doped base layer of the structure, L is the ambipolar diffusion length of charge carriers in the base layer), the charge carrier lifetime tau and the saturation current j(sn) and j(sp) of the highly doped p(+) and n(+) layers. (C) 1998 Elsevier Science Ltd. All rights reserved.