Current analysis of ion implanted p(+)/n 4H-SiC junctions: post-implantation annealing in Ar ambient

An n-type 8 degrees off-axis < 0001 > 4H-SiC epitaxial wafer was processed. The n-type epilayer had doping and thickness of, respectively, similar to 3 x 10(15) cm(-3) and similar to 5 mu m. p(+)/n diodes with not terminated junctions were constructed by a selective area implantation process of 9.2 x 10(14) cm(-2) Al+ ions at 400 degrees C. The diodes had areas in the range 2x10(-4)-1 x 10(-3) cm(2). The Al depth profile was 6x10(19) cm(-3) high and 164 nm thick. The post implantation annealing process was done in a high purity Ar ambient at 1600 degrees C for 30 min. The diode current-voltage characteristics were measured in the temperature range 25-290 degrees C. Statistics of 50-100 measurements per device type were done. The fraction of diodes that could be modeled as abrupt junctions within the frame of the Shockley theory decreased with increasing area value, but was always >= 75%. The ideality factor was >= 2 only at temperatures >= 200 degrees C and bias values <= 1 V. The leakage current was extremely weak and remained of the order of 10(-9) Acm(-2) at 70 degrees C and 500 V reverse bias. 4% of the diodes reached the theoretical voltage breakdown that was 1030 V. The surface roughness of un-implanted and implanted regions after diode processing was, respectively, 2 nm and 12 nm.