Small signal equivalent circuit of unsymmetrical junction diodes at high current densities

Abstract

Finite difference equation methods and lumped models are applied to the solution of the differential equations for the carrier flow through a quasi-neutral semiconductor bulk region at low, moderate and high injection densities. An unsymmetrically doped diode is approximated by a single section lumped model. The static I-V characteristics for this model at low and high current densities are derived. The small signal equivalent circuit of an unsymmetrically doped diode at high injection densities is presented. Approximations for the elements ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R, L, C</tex> ) of this equivalent circuit are calculated from the single section lumped model. The static characteristic and the small signal equivalent circuit elements are in satisfactory agreements with experimental results for diodes in which the base length is not too long compared to the diffusion length.