Characterisation of epitaxial SiC Schottky barriers as particle detectors

Epitaxial SiC devices have been tested as radiation detectors for minimum ionising particles. The devices used are based on a commercial 4H–SiC epitaxial n-type layer deposited onto a 4H–SiC n+ type substrate wafer doped with nitrogen. Single-pad Schottky contacts have been produced by deposition of a 1000-Å gold film on the epitaxial layer using a lift-off technology and ohmic contacts have been deposited on the rear substrate side. The capacitance–voltage characteristics have been measured to determine the net effective doping in the space charge layer and the maximum active thickness of the devices. The measurements showed possible non-uniformity in the net doping of the epitaxial layer. The charge collection efficiency (CCE) has been tested by means of a 0.1 mCi 90Sr β-source. A 100% CCE is measured at the maximum active thickness, which is achieved above approximately 400 V. The charge signal of the SiC devices is stable and reproducible, with no evidence of priming or polarisation effects, due to the high crystalline quality of the epitaxial layer.