Study of bulk and elementary screw dislocation assisted reverse breakdown in low-voltage (< 250 V) 4H-SiC p(+)n junction diodes - Part I: DC properties

Given the high-density (similar to 10(4) cm(-2)) of elementary screw disloc ations (Burgers vector = Ic with no hollow core) in commercial SIC wafers a nd epilayers, all large current (>1 A) SIC power devices will likely contai n elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularl y in high-field vertical power device topologies where SiC is expected to e nable large performance improvements in solid-state high-power systems, Thi s paper compares the de-measured reverse-breakdown characteristics of low-v oltage (<250 V) small-area (<5 x 10(-4) cm(2)) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softe r reverse breakdown current-voltage (I-V) knees, and highly localized micro plasmic breakdown current filaments compared to screw dislocation-free devi ces. The observed localized 4H-SiC breakdown parallels microplasmic breakdo wn observed in silicon and other semiconductors, in which space-charge effe cts limit current conduction through the local microplasma as reverse bias is increased.