"Paradoxes" of carrier lifetime measurements in high-voltage SiC diodes

For Silicon Carbide (SiC) high-voltage rectifier diodes, contradictions app ear when the most important parameter of the diodes, the minority carrier l ifetime, is measured by different techniques. A qualitative analysis and a computer simulation have been carried out to clarify the origin of these co ntradictions. For 4H-SiC p(+) n diodes with 6-kV blocking capability, data on residual voltage drop at high current densities, switch-on time, reverse current recovery, and post-injection voltage decay are analyzed. It is sho wn that the whole set of experimental data can be explained by the existenc e of a thin (l similar to 0.1 mum) layer near the metallurgical boundary of the p+ n junction with very small carrier lifetime eta that is essentially smaller than the carrier lifetime tau across the remaining part of the 50- mum n-base, It is emphasized that the existence of such a layer allows, und er certain conditions, the combination of a relatively Low residual forward voltage drop and very fast reverse recovery. Approaches to minority carrie r lifetime measurements are discussed.