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Semiconductor Photon Detectors Ulrich Parzefall Universität Freiburg

Explore groundbreaking semiconductor detectors for efficient photon detection, covering Si, CdTe, 3D detectors, and Medipix concept. Learn about Si strip detectors and their operation, advanced pixel detectors like MAPS, and the innovative concept of 3D DDTC detectors. Discover the latest research and results in the field of semiconductor photon detection.

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Semiconductor Photon Detectors Ulrich Parzefall Universität Freiburg

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  1. Semiconductor Photon Detectors Ulrich Parzefall Universität Freiburg

  2. Overview • Intro: Semiconductor Detectors • Detector Materials • Silicon • CdTe • Summary and Outlook Ulrich Parzefall, Universität Freiburg

  3. Basic Silicon Strip Detector - + n+-type back side -+ +- +- -+ +- -+ +- -+ p-type surface implants • Take a diode (p-n-junction) • Segment it into strips and n+-dope back side • Apply bias voltage • Wait for photon to deposit charge • Conversion: e- h+ pairs are created • Separated by E-field • Drift towards electrodes • Create signal in p-strips n-type Si-Bulk Ulrich Parzefall, Universität Freiburg

  4. Operation of Si Detector - • MIP deposits 4fC in 300μm Si (23000 e-h+-pairs) • Free charge in 1 cm2 Si-detector is 104 that (T=300K) • Detector can only operate under reverse bias which removes free charges • Depletion zone starts at p-n-junction around strips and grows towards n+-back side + Ulrich Parzefall, Universität Freiburg

  5. Si-Strip Detector Example Ulrich Parzefall, Universität Freiburg

  6. Example: ATLAS SCT Module Ulrich Parzefall, Universität Freiburg

  7. Pixel Detector Overview HAPS design principle • Different pixel detector types • Hybrid Active Pixel Sensors (HAPS) • Detector and readout ASIC are sandwiched together (Nreadout = Npixel ) • Limitation from readout: Pixel size > 120 x 120 μm (2004) • Used widely in collider experiments • ATLAS: 100M Pixels (50x400μm2) • CMS: 23M Pixels (150x150μm2) • Monolithic Active Pixel Sensors (MAPS) • Preamplifier integrated into detector, ASIC nearby • Pixel size > 15 x 15 μm (2005) • Current research topic in many groups, (MIMOSA IReS Strasbourg) Ulrich Parzefall, Universität Freiburg

  8. Medipix Concept e h + HV - • Hybrid principle with sensor and readout ASIC sandwiched • Detector for X-rays • Aim: Replace traditional X-ray photography X-ray Ulrich Parzefall, Universität Freiburg

  9. Semiconductor Detector Material • Material needs to be adapted to photon energy • Absorption for X-rays crucial for detector material • Si only works for low energy X-rays up to ~60 keV • CdTe good up to ~300keV • Medipix-CdTe hot R&D topic Ulrich Parzefall, Universität Freiburg

  10. 3D Detectors n-columns p-columns wafer surface PLANAR 3D p+ p+ p+ n+ 50 mm - n-type substrate - 300 mm - - - - - - - - + + + + + + + + + + • “3D” Principle • narrow columns into detector • diameter 10mm, distance: 50 - 100mm • Effects • lower depletion voltage • smaller charge collection distance -> reduced trapping! 3D concept introduced by: S.I. Parker et al., NIMA 395 (1997) 328 Ulrich Parzefall, Universität Freiburg

  11. 3D Detectors • 3Ds generally complex to manufacture (price) • Different 3D designs exist • This talk restricted to Double-sided Double-Type-Column (DDTC) design • Simplification of full 3D • Made by CNM (Barcelona) and FBK (Trento) • Efficiency is big issue • Field has large variations across detector • Columns are hollow • Must study uniformity of efficiency Ulrich Parzefall, Universität Freiburg

  12. Efficiency in 3D DDTC • Make 2D efficiency map for unirradiated DDTC • Signal cut: SNR ≥ 5 (corresponds to ≈ 6500 e-, 1 fC) • Small efficiency dips in columns • OK – there is no silicon there • Overall efficiency: 99.8 % • 3D DDTC is fully functional as particle detector back column front column readout strips Ulrich Parzefall, Universität Freiburg

  13. Efficiency in 3D DDTC • Cut harder into the signal to look for structure (double cut) • Re-make 2D efficiency map for unirradiated DDTC • Signal cut: SNR ≥ 10 (corresponds to ≈ 13k e-, 2 fC) • Columns become clearly visible • Not a surprise as there is no silicon in columns • Signal comes from Si above/below column • Overall efficiency: 98.5 % • 3D DDTC is fully functional back column front column readout strips Ulrich Parzefall, Universität Freiburg

  14. 3D Detector Results • Compare 3D detectors before and after irradiation to 2·1015Neq in CERN MIP testbeam • Post-irradiation signal larger than expected from 150V onwards => Charge multiplication • Also observed in planar detectors but at much higher bias voltages (Ubias>1.5kV) • ATLAS Si strip upgrade has 500V bias limit • Can „gain“ be used in detector systems ? • Direct comparison: 3D vs planar with MIPs ATLAS planar Si stripHamamatsu detectors 3D DDTC detectorsfrom CNM Ulrich Parzefall, Universität Freiburg

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  16. Ulrich Parzefall, Universität Freiburg

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