Avalanche behaviour and its temperature dependence of commercial SiC MPS diodes: Influence of design and voltage class

The avalanche behavior of 650V and 1200V SiC Merged-PN-Schottky diodes was investigated as function of temperature by means of electrical measurements, simulation and optical detection of the avalanche rated electroluminescence. A very good fit between the simulated and experimentally determined breakdown field strengths could be achieved. The TC of the avalanche was 0.14V/K resp. 0.35V/K for the 650V and 1200V devices. For both voltage classes E Br was ~3.3MV/cm, clearly above the value of 2.5MV/cm which is frequently assumed in literature for 4H SiC. The devices can withstand long term continuous avalanche as well as single pulse avalanche with a junction temperature rise of ~200°C. Finally the observations are compared with the avalanche behavior of SiC JFETs. As expected, these FETs show comparable T-dependence and electroluminescence patterns as the diodes.