Understanding Snap-Off Phenomenon during Reverse Recovery in SiC MOSFET Body Diodes

This work presents a detailed investigation of the reverse recovery behaviour in 1200 V SiC MOSFET body diodes. Unlike modern Si-pin diodes which are optimised for soft reverse recovery, the SiC-body diode exhibits distinctly snappy behaviour as temperature and load current rises. A study is conducted to understand the mechanisms governing snap-off in the SiC-body diode under high temperature and high current regime. Since the snappiness of the diode is attributed to bipolar behaviour and associated plasma removal dynamics, TCAD simulations are utilised to explain the mechanisms behind the snappy behaviour of the diode as seen in measurements. The associated snap-off voltage (V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sn</inf>) is extracted experimentally and shown to be in good agreement with an analytical model. Furthermore, the influence of application relevant parameters, including dead-time and off-state gate voltage, on the reverse recovery characteristics and diode snappiness are analysed.