A Simulation Study of a Novel Superjunction MOSFET Embedded With an Ultrasoft Reverse-Recovery Body Diode

In this paper, a novel superjunction (SJ) MOSFET embedded with an ultrasoft reverse-recovery body diode is proposed and studied by simulation. The device has a composite assistant layer, which consists of a highly doped n-buffer region and an extended p-pillar region, under the SJ layer. The assistant layer provides residual carriers during the reverse-recovery procedure and smoothens the current. Simulated results show that the soft factor is upgraded from 0.04 to over 0.3 when the depth of the assistant layer increases from 0 μm to that of the SJ layer. The increment of the specific ON-resistance is less than 10% if the concentration of the n-buffer region is 25 fold that of the n-pillar region.