  We give a full description of the numerical solution of a general charge
transport model for doped disordered semiconductors with arbitrary field- and
density-dependent mobilities. We propose a suitable scaling scheme and
generalize the Gummel iterative procedure, giving both the discretization and
linearization of the van Roosbroeck equations for the case when the generalized
Einstein relation holds. We show that conventional iterations are unstable for
problems with high doping, whereas the generalized scheme converges. The method
also offers a significant increase in efficiency when the injection is large
and reproduces known results where conventional methods converge.
