Reverse characteristics of pn diodes on 4H-SiC(000-1) C and (11-20) face

We fabricated pn diodes on the 4H-SiC(000-1) C and (11-20) face. The epitaxial growth of the n-type drift layer was carried out in chemical vapor deposition (CVD) reactor under the optimized conditions for each substrate. The pn junction was formed by Al+ ion implantation with multiple energy implantation (30-200 kV) at 600 deg. C subsequent annealing at 1600 deg. C for 5 min in Ar ambient. In the case of the diode on the (000-1) C face, we observed an abrupt avalanche breakdown, which is very similar to the case of the (0001) Si face, at the theoretical breakdown voltage (1150 V) calculated from the doping concentration and the thickness of the drift layer. This result means that there is no difference in the quality of the epitaxial layer between the (0001) Si and the (000-1) C face. On the other hand, a lower breakdown voltage (1200 V) than the theoretical value (1900 V) was observed in the case of the diode on the (11-20) face, and moreover, serious reverse leakage current was also observed. On the basis of the observation of the light emission under the reverse bias, we presume that the crystal defects, parallel to the <11-20> direction, lead to such a high leakage current under the reverse bias