Advanced Radiation Detectors for Particle Physics and Medical Imaging

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2022-11-25
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Authors

Date

2022

Department

Elektroniikan ja nanotekniikan laitos
Department of Electronics and Nanoengineering

Major/Subject

Mcode

Degree programme

Language

en

Pages

62 + app. 76

Series

Aalto University publication series DOCTORAL THESES, 154/2022

Abstract

The edgeless or active edge pixel detector has gained increasingly attention due to its superiority in defect-free edges and the capability to minimize the insensitive area at edges of the detector. The main focus of this thesis is design, fabrication and characterization of edgeless radiation detectors aiming for large area detection of high energy physics and medical imaging applications. Edgeless detectors with various polarities are fabricated on Float Zone silicon and Magnetic Czochralski silicon (MCz-Si). Characterization of edgeless detectors is performed with the electrical and isotope measurement apparatus built by the author at VTT, the 3-D spatial scanning system at IEAP-CTU in Prague, and the proton beam test setup at the Van de Graaff accelerator laboratory. The leakage currents are 1-100 nA/cm2 at full depletion voltages for detectors with different thicknesses. Charge collection efficiency of edge pixels in a detector is influenced by electric field distortion that is mainly determined by detector thicknesses and edge-to-pixel distances. Spectroscopic measurements show good energy resolutions of the edge pixels, indicating an excellent charge collection at the edge of the detector. Apart from edgeless detectors, the author investigates radiation-hard AC-coupled stripe detectors for high-luminosity radiation environments. The detectors are fabricated on MCz-Si wafers with an optimized process to avoid generation of thermal donors. The detectors have full depletion voltages in the range of 120-150 V and leakage currents about 55 nA/cm2 at 200 V bias voltage. The test beam result shows a signal-to-noise ratio greater than 40 achieved by the detector under study. The result demonstrates that MCz-Si detectors can reliably be manufactured in the industrial scale semiconductor process. As a part of the thesis work, a reactor based on the Chloride Vapor Phase Epitaxy technique is built to grow high-purity gallium arsenide (GaAs) epitaxial material. Diodes and pixel detectors are fabricated on an epitaxial GaAs substrate. The full depletion voltage of the GaAs detector with 110 μm epi-layer thickness is in the range of 8–15 V and the leakage current density is about 10 nA/cm2. Good spectroscopic results are obtained from both a GaAs diode and a hybridized Medipix GaAs detector.

Description

Supervising professor

Savin, Hele, Prof., Aalto University, Department of Electronics and Nanoeng, Finland

Thesis advisor

Kalliopuska, Juha, Dr., Advacam Oy, Finland
Härkönen, Jaakko, Dr., Helsinki Institute of Physics, Finland

Keywords

edgeless detector, pixel detector, MCz-Si, GaAs

Other note

Parts

  • [Publication 1]: X. Wu; J. Kalliopuska; S. Eränen; T. Virolainen. “Recent advances in processing and characterization of edgeless detectors”, Journal of Instrumentation, 2012. 7 C02001.
    DOI: 10.1088/1748-0221/7/02/C02001 View at publisher
  • [Publication 2]: J. Kalliopuska, X. Wu, J. Jakubek, S. Eränen, T. Virolainen, “Processing and characterization of edgeless radiation detector for large area detection”, Nuclear Instruments and Methods in Physics Research A, 2013. 731: pp. 205-209.
    DOI: 10.1016/j.nima.2013.06.097 View at publisher
  • [Publication 3]: X. Wu, J. Härkönen, S. Eränen, J. Kalliopuska, T. Mäenpää, P. Luukka, A. Karadzhinova, E. Tuovinen, L. Spiegel, A. Oja, A. Haapalinna, “Strip Detectors Processed on High-Resistivity 6-inch Diameter Magnetic Czochralski Silicon (MCz-Si) Substrates”, IEEE Transactions on Nuclear Science, 2014. 61(1): pp. 611-618.
    DOI: 10.1109/TNS.2013.2295430 View at publisher
  • [Publication 4]: X. Wu, J. Kalliopuska, M. Jakubek, J. Jakubek, A. Gädda, S. Eränen, “Study of edgeless radiation detector with 3D spatial mapping technique”, Journal of Instrumentation, 2014. 9 C04004.
    DOI: 10.1088/1748-0221/9/04/C04004 View at publisher
  • [Publication 5]: X. Wu, P. Kostamo, A. Gädda, S. Nenonen, T. Riekkinen, J. Härkönen, H. Andersson, Y. Zhiyaev, J. Salonen, S. Eränen, M. Mattila, H. Lipsanen, M. Prunnila, J. Kalliopuska, A. Oja, “Radiation detector fabricated on high-purity GaAs epitaxial materials”, Journal of Instrumentation, 2014. 9 C12024.
    DOI: 10.1088/1748-0221/9/12/C12024 View at publisher
  • [Publication 6]: X. Wu, T. Peltola, T. Arsenovich, A. Gädda, J. Härkönen, A. Junkes, A. Karadzhinova, P. Kostamo, H. Lipsanen, P. Luukka, M. Mattila, S. Nenonen, T. Riekkinen, E. Tuominen, A. Winkler, “Processing and characterization of epitaxial GaAs radiation detectors”, Nuclear Instruments and Methods in Physics Research A, 2015. 796: pp. 51-55.
    DOI: 10.1016/j.nima.2015.03.028 View at publisher
  • [Publication 7]: T. Peltola, X. Wu, J. Kalliopuska, C. Granja, J. Jakubek, M. Jakubek, J. Härkönen, A. Gädda, “Characterization of thin p-on-p radiation detectors with active edges”, Nuclear Instruments and Methods in Physics Research A, 2016. 813: pp. 139-146.
    DOI: 10.1016/j.nima.2016.01.016 View at publisher

Citation

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https://urn.fi/URN:ISBN:978-952-64-0993-1

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[diss] Sähkötekniikan korkeakoulu / ELEC