Improved turn-off capability of IGBT with LIHT structure

LIHT (Lack Injection of Hole Termination) structure is proposed and studied. Compared with conventional termination structure, the novel structure features a partial N-doped anode in the transition region and termination region instead of a whole P-doped anode. The LIHT structure stores less carries in the drift region of the transition region and termination region, in which holes concentration reduced by 3 orders of magnitude that from 10
¹⁴
cm
^-3
in conventional structure to 10
¹¹
cm
^-3
. It will decrease the holes quantity need to be extracted from the transition region when turning the IGBT off and avoid the existence of hole current crowding at the corner of the guard ring. With the LIHT structure, the risen lattice temperature is reduced by 27.5K during turn-off compared with conventional structure. Therefore the LIHT structure eliminates the phenomenon of over-current and over-temperature in the transition region, which makes the device own ultra robust turn-off capability. Based on the concept of current crowding effect, the authors attempt to propose a thermal runaway failure (TRF) model to predict the maximum current can be turned off.