HIGH-LEVEL INJECTION PHENOMENA IN P-N-JUNCTIONS

To model high injection phenomena in P-N junction devices it is usuall y necessary to use numerical analysis. This is because the standard pr ocedure of dividing the structure into neutral zones and depletion lay er (regional approximation) fails. In a recent paper, Yue et al. [J. A ppl. Phys. 77, 1611 (1995)] proposed an extension of the Shockley theo ry, retaining the form of the conventional diffusion current-only mode l for the conduction mechanism. Their solution was based on the resolu tion of the ambipolar transport equation in the base. It is shown here by a numerical simulation of the complete structure, within the frame work of the drift-diffusion model, that both the exponential current d ependence: J alpha exp(eVa/2kT) as well as the Yue et al. approximatio n are valid only in the limiting case of a strongly extrinsic short ba se diode. (C) 1996 American Institute of Physics.