Analyzing charge distribution in the termination area of 4H-SiC diodes by measuring depletion-layer capacitance

The distribution of positive-charge density at the SiO2/SiC interface of the termination area (QTM) was analyzed by measuring the depletion-layer capacitance of 4H-SiC PN diodes with different termination structures. A change in QTM induced by reverse-bias stressing (ΔQTM) caused a change in the breakdown voltage of the diodes. By comparing the measured depletion-layer capacitance to the simulated value, the initial QTM () and the distribution of ΔQTM were clarified. It is concluded from these results that the distribution of ΔQTM was not uniform but that positive charges mostly accumulated in the termination area under a high applied electric field.