Particle detectors based on semi-insulating silicon carbide

Particle detectors were made using semi-insulating 4H-SiC as the detection medium. Devices produced with this material have the possibility of being extremely radiation hard. For the purposes of building radiation hard detectors, the parameters of interest are the large band gap and low intrinsic carrier density which implies low leakage currents, the large resistivity that allows ohmic contacts to be used to sense the charge created during ionisation, the large breakdown voltage that gives stable operation, and the large cohesive energy and tightly bound structure which imply good radiation resistance. The investigated photoconductivity detectors are formed by ohmic contacts (Al) on the front- and back-side of a 310 mu m thick semi-insulating 4H-SiC substrate from Cree. These structures of contacts are ranging from 1 - 3 mm in diameter and have a guard ring structure to prevent edge leakage currents. From the I-V characteristic a substrate resistivity of 5.1.10(10) Omega cm was determined. The detectors respond to beta-particles similar as detectors made of diamond. Signal heights of about 2000 e(-) were achieved for quasi minimum ionising electrons. First radiation hardness tests shows an increase of the substrate resistivity by a factor three after a proton (3 GeV) fluence of 4.16.10(14) cm(-2) and a reduction of the signal height of about 23%. The results indicate the feasibility of using silicon carbide as detection medium for particle detectors. Future developments of SiC-detectors with applications in particle physics experiments and other fields are discussed.