Tunneling Current in 4H-SiC p-n Junction Diodes

Heavily doped 4H-silicon carbide (SiC) epitaxial p-n junction diodes are fabricated, and their tunneling current under reverse-biased condition is investigated. Soft increase of the leakage current before avalanche breakdown is observed in the diodes with heavy reduced doping concentration. The temperature and electric field strength dependencies of the leakage current reveal that the leakage current is caused by a phonon-assisted tunneling process. An accurate parameter set for simulating the phonon-assisted tunneling current in 4H-SiC is obtained, which agrees well with the experimental results within a wide temperature range (100-500 K) regardless of the reduced doping concentration. In 4H-SiC p-n junction diodes, the Zener breakdown occurs at the maximum electric field strength of 5.7 MV/cm.