William Cunningham Properties of SiC radiation detectors W. Cunningham a, J. Melone a, V.Kazukauskas b,c P. Roy a, F. Doherty a, M. Glaser d, J.Vaitkus b,c, M. Rahman a a Dept. of Physics & Astronomy, University of Glasgow, Glasgow, G12 8QQ, Scotland b Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al.9-III, 2040 Vilnius, Lithuania c Faculty of Physics, Vilnius University, Sauletekio al.9-III, 2040 Vilnius, Lithuania d EP Division, CERN, CH-1211 Geneva 23, Switzerland

William Cunningham Outline of talk Properties of SiC Details of samples Spectra- pre-irradiation Analysis of spectra and material Post- irradiation data Future work and conclusions

William Cunningham Properties of SiC for detector purposes Wide bandgap 3.3 eV High physical strength, chemical inertness High binding energy

William Cunningham Properties of SiC for detector purposes (cont.) Semi-insulating material has very high device resistivity >  cm High breakdown field Low leakage current ~10 -8 Acm -2 at -600 V

William Cunningham Test samples Schottky barrier diode on 4-H Semi-insulating SiC Pad and guard ring 100nm Ti Back contact 100nm Ni 200 nm Si 3 N 4 for surface passivation Pad and guard ring Back face contact Si 3 N 4 passivation Bulk S.I. SiC 100  m thick

William Cunningham Pre-irradiation spectra Spectra taken for 5.48 MeV Am 241  particles max CCE 60% at -600V Large low energy tail

William Cunningham Where's the missing charge? No loss of energy measurements taken in vacuum. All energy deposited in detector samples 100  m thick, Am 241  particles travel ~  m in SiC. There must be some other explanation.

William Cunningham ‘Where is the missing charge’ part 1 Current decay time Time constants t1 = 4.2s t2 = 15.3s t3 = 125.3s R 2 =0.999

William Cunningham What is Thermally Stimulated Current (TSC) Sample cooled using liquid N 2 Sample warms to room temp (~300 K) Increasing temp thermally activates defects –i.e. impurities, crystal defects etc plotting I against 1/T allows calculation of defect activation energies

William Cunningham ‘Where is the missing charge’part 2 Thermally stimulated Current TSC measurement of SiC diode, peaks indicate trap activation energy

William Cunningham Identification of trap levels T (K)Ea (eV)Identification Localised dislocation Sghaier et al Localised dislocation Sghaier et al Hexagonal lattice point C vacancy Bechstedt et al Vanadium activation Reshanov et al

William Cunningham Post-irradiation data, part 1 ‘Change in leakage current’ Post irradiation reverse J-V characteristics

William Cunningham Post-irradiation data, part 2 ‘Change in measured spectra ’ Fluence pions/cm -2 breakdown at 550 V

William Cunningham Post-irradiation data, part 2 ‘Change in measured spectra ’ Fluence pions/cm -2 breakdown at 550 V

William Cunningham Post-irradiation data, part 2 ‘Change in measured spectra ’ Relative peak for positions maximum CCE

William Cunningham Future work, or ‘How can we get the charge out’ Work to continue developing contacts Deeper investigation into defects and trap levels Experimentation with detector thickness to increase applicable bias volts. Active area size to be examine