Gate field emission induced breakdown in power SiC MESFETs

Abstract
The breakdown mechanism of SiC MESFETs has been analyzed by careful investigation of gate leakage current characteristics. It is proposed that gate current-induced avalanche breakdown, rather than drain avalanche breakdown, is the dominant failure mechanism for SiC MESFETs: thermionic-field emission and field emission are dominant for the ON state (above pinch-off voltage) and the OFF state (below pinch-off voltage), respectively. The effect of Si/sub 3/N/sub 4/ passivation on breakdown voltage has been also investigated. Si/sub 3/N/sub 4/ passivation decreases the breakdown voltage due to higher electric field at the gate edge compared to edge fields before passivation. A reduction in surface trapping effects after passivation results in the higher electric field because the depletion region formed by trapped electrons is reduced significantly.

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