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

William Cunningham

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

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