Measuring depletion-layer capacitance to analyze a decrease in breakdown voltage of 4H-SiC diodes

Abstract

A decrease in breakdown voltage (VBD) in the termination area of 4H-SiC PN diodes after 64 h reverse-bias stressing was analyzed. To analyze the VBD decrease, a novel analysis method based on the results of measuring depletion-layer capacitance of the PN diodes was proposed. The measurement results indicate that the positive-charge density (QTM) at the SiO2/SiC interface of the termination area increased after the reverse-bias stressing. Besides, in the case of QTM of 1012 cm−2 at the SiO2/SiC interface, the decrease in the measured capacitance showed the same tendency as the decrease in the simulated capacitance. By comparing the measured full depletion voltage and simulated full depletion voltage, the amount of QTM was estimated. It is thus concluded that the proposed method for measuring the depletion-layer capacitance is effective for analyzing the QTM change in the termination area.