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
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William Cunningham
Properties of SiC radiation detectors
W. Cunningham a, J. Melone a, V.Kazukauskasb,c P. Roy a, F. Doherty a, M. Glaser d, J.Vaitkusb,c, M. Rahman a
a Dept. of Physics & Astronomy, University of Glasgow, Glasgow, G12 8QQ, ScotlandbInstitute of Materials Science and Applied Research, Vilnius University, Sauletekio al.9-III, 2040 Vilnius, LithuaniacFaculty of Physics, Vilnius University, Sauletekio al.9-III, 2040 Vilnius, LithuaniadEP Division, CERN, CH-1211 Geneva 23, Switzerland
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Outline of talk
• Properties of SiC
• Details of samples
• Spectra- pre-irradiation
• Analysis of spectra and material
• Post- irradiation data
• Future work and conclusions
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Properties of SiC for detector purposes
• Wide bandgap 3.3 eV
• High physical strength, chemical inertness
• High binding energy
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Properties of SiC for detector purposes (cont.)
• Semi-insulating material has very high device resistivity > 1011 cm
• High breakdown field
• Low leakage current ~10-8 Acm-2 at -600 V
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Test samples
• Schottky barrier diode on 4-H Semi-insulating SiC
• Pad and guard ring 100nm Ti
• Back contact 100nm Ni
• 200 nm Si3N4 for surface passivation
Pad and guard ring
Back face contact
Si3N4
passivation
Bulk S.I. SiC100 m thick
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Pre-irradiation spectra
Spectra taken for 5.48 MeV Am241 particles max CCE 60% at -600V
Large low energy tail
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Where's the missing charge?
• No loss of energy measurements taken in vacuum.
• All energy deposited in detector samples 100 m thick, Am241 particles travel ~10-20 m in SiC.
• There must be some other explanation.
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‘Where is the missing charge’ part 1 Current decay time
Time constantst1 = 4.2st2 = 15.3st3 = 125.3s R2 =0.999
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What is Thermally Stimulated Current (TSC)
• Sample cooled using liquid N2
• 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
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‘Where is the missing charge’part 2Thermally stimulated Current
TSC measurement of SiC diode, peaks indicate trap activation energy
4
3 2
1
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Identification of trap levels
T (K) Ea (eV) Identification
118 0.32 Localised dislocationSghaier et al
135 0.39 Localised dislocationSghaier et al
200 0.63 Hexagonal lattice point C vacancyBechstedt et al
260 0.92 Vanadium activationReshanov et al
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Post-irradiation data, part 1‘Change in leakage current’
Post irradiation reverse J-V characteristics
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Post-irradiation data, part 2‘Change in measured spectra ’
Fluence 1012 pions/cm-2
breakdown at 550 V
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Post-irradiation data, part 2‘Change in measured spectra ’
Fluence 1013 pions/cm-2
breakdown at 550 V
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Post-irradiation data, part 2‘Change in measured spectra ’
Relative peak for positionsmaximum CCE
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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
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