Enhancement of carrier lifetime in lightly Al-doped p-type 4H-SiC epitaxial layers by combination of thermal oxidation and hydrogen annealing

We investigated the enhancement of carrier lifetime in lightly Al-doped p-type 4H-SiC epilayers (N-A similar or equal to 2 x 10(14) cm(-3)) by postgrowth processing. A carrier lifetime of 2.8 mu s in an as-grown epilayer is increased to 5.1 mu s by carbon vacancy elimination, i.e., thermal oxidation at 1400 degrees C for 48 h. It reaches 10 mu s by subsequent hydrogen annealing at 1000 degrees C for 10 min. The carrier lifetime in the as-grown epilayer is also increased to 4.0 mu s by only hydrogen annealing. These results suggest that, in addition to carbon vacancy, there is another lifetime killer in p-type SiC, which cannot be eliminated by thermal oxidation but can be passivated by hydrogen annealing. (C) 2014 The Japan Society of Applied Physics