Trench IGBT with stepped doped collector for low energy loss

Abstract

In this paper, a novel technique of variation doping profile in collector region for trench IGBT is proposed. The collector region is segregated in three sections such that the section with higher concentration lies towards emitter side while section with lower concentration lie towards gate side. The presence of lightly doped collector section increases the recombination rate by injecting lesser charge carrier leading to reduction in carrier lifetime. This effect further improves turn-off process for proposed device. However, due to increased recombination rate, collector current density reduces. But, this reduction is counter balanced by heavily doped collector section which injects higher charge carriers and maintains current flow through proposed device. The electrical characteristics of proposed and conventional device is simulated and analyzed. It is inferred that proposed device exhibits 48% reduction in turn-off time further minimizing energy loss by 53.3%. The lower doping profile of collector region also reduces corner electric field but due to p++-col section the net electric field increases hence, improving the breakdown voltage by 8.7%. Additionally, proposed structure exhibits 16.7% increment in Baliga figure of merit as compared to conventional design.