Stability of 4H-SiC JBS Diodes under Repetitive Avalanche Stress

Silicon carbide (SiC) Junction Barrier Schottky (JBS) rectifiers, used as antiparallel diodes for silicon IGBTs, can be subjected to high current reverse avalanche stress (RAS) during operation in inductive load circuits. The stability of commercially available and NCSU SiC JBS rectifiers was investigated after repetitive RAS. No degradation was observed after 10,000 RAS pulses at the rated on-state current level. Numerical Simulations reveal that the degradation of JBS diodes is suppressed because: (a) the electric field at the Schottky contact is reduced by P+ shielding region, (b) the avalanche current primarily flows via the P+ shielding region and not the Schottky contact, and (c) the temperature rise is limited to less than 100 degrees C during the stress. The avalanche energy for failure of the diodes was also obtained for three values of load inductance by increasing the avalanche current. The critical failure energy was found to be independent of the load inductance values leading to a reduction of the failure current with increasing load inductance.