Excess carrier density and forward voltage drop in trench insulated gate bipolar transistor (TIGBT)

Decrease in the forward voltage drop due to the enhanced carrier density at the cathode side of the trench insulated gate transistor (TIGBT) is studied as a function of the aspect ratio between the accumulation layer and cell size as well as the applied gate voltage and compared with those for the planar DMOS-IGBT. Based on analytical expressions for hole density distribution in the lateral and vertical directions in the proximity of the reverse biased cathode junction, the current gain for the pnp transistor action is determined. The analytical results show a fair agreement with the numerical simulations using MEDICI.