Analytical model of the effective recombination velocity of diffused p− p+ ( n− n+) high-low junctions at arbitrary injection level

Abstract

This paper proposes an analytical model of the minority carrier transport across p− p + ( n− n +) high-low junctions, which is used to study the physical factors affecting the injection dependence of the effective recombination velocity (ERV) of such structures. In particular analytical expressions, valid at any injection level, of the recombination factors of the space charge region and of the quasi-neutral region of the junction are presented. The model is based on an original extension of the continuity equation written in terms of the minority-effective majority carrier product, which allows to describe the simultaneous occurrence of heavy doping and high injection effects. Comparison of this model with experiments and computer simulations indicates that the injection dependence of ERV starts to saturate as the injection level reaches the onset doping value of the heavy doping effects. The above model is shown to explain ERV measurements carried out on n− n + junctions of different thickness and for a wide range of injection levels.