Suppression the Bipolar Degradation of 4H-SiC PiN Diodes by Growing Recombination-Enhancing Buffer Layers

"Bipolar degradation" phenomenon has severely hindered the development of 4H-SiC bipolar devices. The defect mechanism is the expansion of Shockley-type stacking faults from basal plane dislocations under the condition of electron-hole recombination. Among several approaches, the purpose of growing a recombination-enhancing buffer layer is to prevent the minority carriers of holes to reach the epilayer/substrate interface where a high density of BPD segments exists. In this paper, N-doped, as well as Ti and N co-doped 4H-SiC buffer layers have been grown to shorten the minority carrier lifetimes. The dependence of Ti doping concentration on TiCl
4
flow rate has been determined. 4H-SiC PiN diodes with a N-doped or Ti, N co-doped buffer layer were fabricated and tested with a forward current density of 200 A/cm
²
for 1 hour. The forward voltage drop stability of those diodes with a Ti, N co-doped buffer layer has been greatly improved.