Investigation and Improvement of high performance planar IGBT

In this paper, for the first time, an insulated gate bipolar transistor with an improved buffer is proposed to improve the IGBT losses. The structure of the proposed device is almost identical with that of the conventional IGBT, except for the buffer layer which is formed by employing a very highly doped stripped n+ and a weakly doped n" structure. Compared with the conventional PT-IGBT, the proposed device exhibits a better trade-off relation between the conduction and switching losses. An interesting feature of the improved IGBT is that its on- resistance(on-state losses) can be largely decreased at the expenditure of a moderate and neglectable increase in turn-off time. The weakly doped n" buffer region leads to a high injection efficiency anode providing an optimum level of conductivity modulation required for a given on-state voltage drop in the n- drift region, while the very highly doped n+ buffer region results in a low injection anode accelerating the device turn-off. Detailed physical mechanisms are given.