Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage ( 250 V ) 4 H – SiC p n Junction Diodes — Part I : DC Properties

Given the high-density ( 10 cm ) of elementary screw dislocations (Burgers vector= 1c with no hollow core) in commercial SiC wafers and epilayers, all large current ( >1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the dc-measured reverse-breakdown characteristics of low-voltage ( <250 V) small-area (<5 10 4 cm) 4H–SiC pn diodes with and without elementary screw dislocations. Diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown current–voltage ( I V ) knees, and highly localized microplasmic breakdown current filaments compared to screw dislocation-free devices. The observed localized 4H–SiC breakdown parallels microplasmic breakdown observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.

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