New Insights using Avalanche Mode for On-wafer Evaluation of SiC Diodes Technology and Design Ruggedness

On-wafer measurements of 1200V rated 4H-SiC power diodes have been performed in near avalanche mode to investigate the stability and robustness of the devices. The method consists of biasing the SiC diodes at near-avalanche current or voltage levels for a variable period of time. The drifting of the static electrical parameters (leakage current, avalanche voltage, Schottky barrier height) is then studied. For two different SiC diode processing technologies, two drift behaviors of the blocking I-V curves were observed. Impact ionization, which is responsible for the avalanche phenomenon at high electric fields, has been localized and distinguished between the active region of the devices and the edge termination region, depending on the processing technology. Electroluminescence observations and numerical simulations were performed to confirm the interpretation of the electrical results. The robustness of the method was further supported.