SiC p+n Junction-Diodes toward Beam Monitor Applications

We report on SiC pn-junction diodes with a high blocking voltage over 3 kV. Although SiC radiation sensors have been developed with a Schottky barrier type due to a simple fabrication process in the early stages, pn junction structures are advantageous due to lower sensitivity of the surface defects. Thus, this system provides an ideal condition to investigate the effect of bulk crystal defects on the characteristics of the radiation sensor. The pn diodes were designed with a device simulator and fabricated with a 4-inch 4H-SiC wafer. The epitaxial layer was grown on an n-type substrate with sufficiently low doping concentration of Nd-Na =~ 5 × 1014 cm..3 and an average thickness of 52 μm. Fabricated pn diodes with a relatively large leakage current still show a clear peak of the Landau distribution in the charge spectrum, suggesting their practical availability as minimum ionizing particle detectors. The estimated electron-hole pair creation energy is consistent with the published studies and we expect good radiation tolerance. Feasibility based on the wafer processing indicates that the prototype devices are a good candidate for the muon beam monitor application in the coherent muon-to-electron transition experiment (COMET) at J-PARC.