DESIGN CRITERION AND OPERATION MECHANISM FOR 4.5 KV INJECTION ENHANCED GATE TRANSISTOR

This paper investigates the injection enhancement effect of a trench g ate structure for a metal oxide semiconductor (MOS) controlled power t ransistor called an injection enhanced gate transistor (IEGT), By virt ue of the enhancement in effective electron injection efficiency, 4.5 kV IEGTs attain a thyristor-like carrier profile during the on-state, and hence achieve the same low on-state voltage drop as that of thyris tors, The operation mode of the IEGT was studied using a two-dimension al numerical simulation, and verified by device fabrication, It was co nfirmed that the proposed novel trench gate geometry acts as an inject ion enhancer by restricting the hole diffusion current which flows fro m the n-type high-resistance base layer to the cathode electrode. It i s shown for the first time that the effective electron injection effic iency of the n-ch insulated gate bipolar transistor increases to nearl y 1. It is also shown that the new trench gate structure effectively d ecreases the forward voltage drop without degradation of turn-off capa bility.