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

We fabricated pn diodes on the 4H-SiC(000-1) C-face and (11-20) face. The epitaxial growth of the n-type drift layer was carried out in a low-pressure, horizontal hot-wall type CVD reactor under the optimized conditions for each substrate. The doping concentration and the thickness of the epitaxial layers were 1.6x10(16)cm(-3), 10mum and 4.0x10(15)cm(-3), 11mum for the (000-1) C-face and (11-20) face, respectively. The pn junction was fabricated by Al+ ion implantation with multiple energy implantation (30-200kV) at 600degreesC subsequent to post-annealing at 1600degreesC for 5min 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 (1150V) calculated from the doping concentration and the thickness of the drift layer. On the other hand, a lower breakdown voltage (1200V) than the theoretical value (1900V) 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.