Parasitic Bipolar Action in SiC Power MOSFETs Demonstrated by Two-Photon Laser Experiment

A two-photon absorption technique is explored for Silicon carbide power MOSFETs and power junction barrier Schottky diodes using a pulsed laser. The similarities in design between the specific MOSFETs and diodes tested permit using mechanisms existing in the different structures as explanation for observed current variation with laser position. The diode shows variation in average current with change in laser depth only, whereas the MOSFET shows variation both with shifts in depth and shifts in position across the striped geometry of the device. The variation is explained to be due to bipolar amplification of the charge carriers generated in the MOSFET when a pulse focus includes a channel below a gate. This conclusion is then reinforced using results from prior heavy ion and simulation work done for similar Silicon carbide MOSFETs.