Abstract
To model high injection phenomena in P-N junction devices it is usually necessary to use numerical analysis. This is because the standard procedure of dividing the structure into neutral zones and depletion layer (regional approximation) fails. In a recent paper, Yue et al. [J. Appl. Phys. 77, 1611 (1995)] proposed an extension of the Shockley theory, retaining the form of the conventional diffusion current-only model for the conduction mechanism. Their solution was based on the resolution of the ambipolar transport equation in the base. It is shown here by a numerical simulation of the complete structure, within the framework of the drift-diffusion model, that both the exponential current dependence: J alpha exp(eVa/2kT) as well as the Yue et al. approximation are valid only in the limiting case of a strongly extrinsic short base diode. (C) 1996 American Institute of Physics.