Effect of Postoxidation Nitridation on Forward Current–Voltage Characteristics in 4H–SiC Mesa p-n Diodes Passivated With SiO2

An origin of shunt current, a ledge in forward current-voltage (I-V) characteristics, in 4H-SiC mesa p-n diodes was investigated by adopting various surface passivation processes. Experimental results indicated that the shunt current path is located along the mesa sidewall and the shunt current is enlarged with increasing NO-annealing period and temperature. Based on these results, we qualitatively explain that nitrogen-related positive charges near the SiC/SiO₂ interface, which are formed by postoxidation nitridation, induce band bending and lowering of the diffusion potential along the mesa sidewall, resulting in occurrence of the shunt current.