Interface states and related surface currents in SiC junctions

In the present work an analytical model for the excess surface currents related to the interface states in SiC junctions is proposed. Four contributions to the current are considered: generation of charge carriers associated with surface states localized at the SiC-SiO₂ interface, generation of carriers associated with traps in the depletion layer, the diffusion of carriers in the neutral region near the depletion layer, and the channel effect due to surface charge. The surface charge can cause a surface inversion layer in the low doped region of the diode. In conditions of the reverse bias, a current flows through this region-giving rise to an additionally surface component of the leakage current (surface channel current). Our calculations take into account the incomplete ionization of dopants and use the results of the charge-sheet model for SiC inversion layers. Reported experimental results on surface effects on SiC junctions are considered for the evaluation of the model.