GO SCINT_beta-Ga2O3:Ce semiconductor as a new scintillator - investigation of spectroscopic and scintillation properties

• Applicant: Dr. Zbigniew Galazka
• Subject Area: Experimental Condensed Matter Physics ; Synthesis and Properties of Functional Materials
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 380772227

• Final Report Year: 2022

Final Report Abstract

1) A number of bulk β-Ga2O3 single crystals was grown by the Czochralski method at IKZ, from which crystal samples with a typical size of 5x5x0.5 mm3 were prepared for measurements of scintillation properties at NCU. The crystals were grown at different oxygen concentrations in the growth atmosphere (1 – 35 vol.%), doped with various elements (Ce, Si, Mg, Al, Ce+Si, Ce+Al, Ce+Si+Al), and had different electrical properties ranging from an electrically insulating state, through normal semiconducting state (ne = 2x10^16 – 2x10^18), to highly conducting state (ne = 2x10^18 – 1x10^19 cm-3). 2) The scintillation light yield (LY) of β-Ga2O3 crystal samples under γ-irradiation (662 keV) was found to be dependent on the free electron concentration (ne) only, i.e. it is independent on dopants or growth conditions, in contrast to classical scintillators being electrical insulators. Ce, which is a common scintillation activator, substantially does not affect the scintillation LY or very little (in particular decay time). The maximum of the LY was measured at a low level of ne = 2 – 5x10^16 cm-3, which was achieved for undoped bulk β-Ga2O3 single crystals grown at relatively low oxygen concentration in the growth atmosphere (2 – 4 vol.%). 3) The maximum of the scintillation LY at RT was measured at a level of 8920 ph/MeV, which is very close to a target value claimed in the present project (10000 ph/MeV), with the energy resolution of 9 – 10 %. The decay time is complex with the prompt time constant of 3 – 30 ns, the contribution of which increases (> 20 %) with ne. 4) The scintillation mechanism in β-Ga2O3 is not clear yet, but it is related to the excitonic emission in the spectral region 380 – 420 nm. The scintillation emission overlaps the cathodoluminescence emission which is assigned to self-trapped excitons. 5) The present project has established a direct and clear correlation between scintillation and electrical properties of bulk β-Ga2O3 single crystals grown by the Czochralski method, which constitutes a solid foundation for further development of β-Ga2O3 as a scintillator for radiation detection, which might be also valid for other oxide semiconductors.

Publications

• Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al. Journal of Crystal Growth, 486, 82-90.
  Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin & Bickermann, Matthias
  
• Electrical and optical properties of β -Ga2O3 and β-Ga2O3:Ce crystals
  M. Makowski, M. E. Witkowski, W. Drozdowski, A. J. Wojtowicz, A. Fiedler, K. Irmscher, S. Ganshow, R. Schewski & Z. Galazka
  
• Luminescence Properties of Ga2O3 Crystals Activated withVarious Ions
  M. E. Witkowski, M. Makowski, W. Drozdowski, A. J. Wojtowicz, Z. Galazka, K. IrmscherM. E. Witkowski, M. Makowski, W. Drozdowski, A. J. Wojtowicz, Z. Galazka & K. Irmscher
  
• Symposium in Bydgoszcz, Poland, 10-11 December 2018, „Where Jędrzej Śniadecki Met Jan Czochralski", "Novel Czochralski-Grown Scintillator Materials"
  W. Drozdowski
  
• IR-Laser Induced Emission from X-Ray Excited Pure and Doped β-Ga2O3
  A. J. Wojtowicz, W. Drozdowski, M. Makowski, M. E. Witkowski, R. Schewski & Z. Galazka
  
• IWGO-3, Columbus, USA, 12-15 August 2019“Czochralski-grown bulk β-Ga2O3 single crystals doped with mono-, di-, tri-, and tetravalent ions, and VGF-grown bulk ZnGa2O4 single”
  Z. Galazka
  
• Negative Thermal Quenching of X-Ray Excited Luminescence in Pure and Doped β- Ga2O3
  M. E. Witkowski, W. Drozdowski, M. Makowski, A. J. Wojtowicz, R. Schewski & Z. Galazka
  
• Scintillation Properties of Czochralski-Grown Singly-, Doubly- and Triply-Doped β- Ga2O3 Single Crystals
  M. Makowski, W. Drozdowski, M. E. Witkowski, A. J. Wojtowicz, R. Schewski & Z. Galazka
  
• Semiconductor Scintillator Development: Pure and Doped β-Ga2O3
  W. Drozdowski, M. Makowski, M. E. Witkowski, A. J. Wojtowicz, R. Schewski, K. Irmscher & Z. Galazka
  
• Tailoring the scintillation properties of β-Ga2O3 by doping with Ce and codoping with Si. Optical Materials Express, 9(9), 3738.
  Makowski, Michal; Drozdowski, Winicjusz; Witkowski, Marcin E.; Wojtowicz, Andrzej J.; Irmscher, Klaus; Schewski, Robert & Galazka, Zbigniew
  
• β-Ga2O3:Ce as a fast scintillator: An unclear role of cerium. Radiation Measurements, 121, 49-53.
  Drozdowski, Winicjusz; Makowski, Michał; Witkowski, Marcin E.; Wojtowicz, Andrzej J.; Galazka, Zbigniew; Irmscher, Klaus & Schewski, Robert
  
• Bulk β-Ga2O3 single crystals doped with Ce, Ce+Si, Ce+Al, and Ce+Al+Si for detection of nuclear radiation. Journal of Alloys and Compounds, 818, 152842.
  Galazka, Zbigniew; Schewski, Robert; Irmscher, Klaus; Drozdowski, Winicjusz; Witkowski, Marcin E.; Makowski, Michał; Wojtowicz, Andrzej J.; Hanke, Isabelle M.; Pietsch, Mike; Schulz, Tobias; Klimm, Detlef; Ganschow, Steffen; Dittmar, Andrea; Fiedler, Andreas; Schroeder, Thomas & Bickermann, Matthias
  
• Condensed Matter Physics Seminar at Institute of Physics, Polish Academy of Sciences, Warsaw, Poland (on-line), 27 October 2020 "β-Ga2O3; a New Semiconducting Scintillator"
  A. J. Wojtowicz
  
• Department of Applied Physics Seminar at Institute of Physics, Nicolaus Copernicus University in Toruń, Poland (on-line), 9 December 2020 "The new semiconducting scintillator β-Ga2O3; a delight & challenge"
  A. J. Wojtowicz
  
• Optical and Scintillation Properties of Pure and Doped β-Ga2O3 Crystals
  M. Makowski, W. Drozdowski, M. E. Witkowski, A. J. Wojtowicz, R. Schewski & Z. Galazka
  
• Semiconductor scintillator development: Pure and doped β-Ga2O3. Optical Materials, 105, 109856.
  Drozdowski, Winicjusz; Makowski, Michał; Witkowski, Marcin E.; Wojtowicz, Andrzej J.; Schewski, Robert; Irmscher, Klaus & Galazka, Zbigniew
  
• ACCGE-22, USA (on-line), 2-4 August 2021 “Czochralski growth and physical properties of bulk β-Ga2O3 single crystals”
  Z. Galazka
  
• Bulk single crystals of β-Ga2O3 and Ga-based spinels as ultra-wide bandgap transparent semiconducting oxides. Progress in Crystal Growth and Characterization of Materials, 67(1), 100511.
  Galazka, Zbigniew; Ganschow, Steffen; Irmscher, Klaus; Klimm, Detlef; Albrecht, Martin; Schewski, Robert; Pietsch, Mike; Schulz, Tobias; Dittmar, Andrea; Kwasniewski, Albert; Grueneberg, Raimund; Anooz, Saud Bin; Popp, Andreas; Juda, Uta; Hanke, Isabelle M.; Schroeder, Thomas & Bickermann, Matthias
  
• Colloquium at Institute of Physics, Nicolaus Copernicus University in Toruń, Poland (on-line), 8 April 2021"β-Ga2O3; the New Efficient Semiconducting Scintillator; Is Physics against Us?"
  A. J. Wojtowicz
  
• Development of a New Semiconductive Scintillator: an In-Depth Analysis of Scintillation Properties of Pure and Doped β-Ga2O3 Crystals
  M. Makowski, M. E. Witkowski, A. Bachiri, W. Drozdowski, A. J. Wojtowicz, K. Irmscher, R. Schewski & Z. Galazka
  
• Heading for Brighter and Faster β-Ga2O3 Scintillator Crystals
  W. Drozdowski, M. Makowski, A. Bachiri, M. E. Witkowski, A. J. Wojtowicz, R. Schewski, K. Irmscher & Z. Galazka
  
• Low Temperature Thermoluminescence of β-Ga2O3 Crystals
  K. J. Drozdowski, M. E. Witkowski, M. Makowski, W. Drozdowski, A. J. Wojtowicz, K. Irmscher, R. Schewski & Z. Galazka
  
• Low Temperature Thermoluminescence of β-Ga2O3 Scintillator – New Results and New Interpretations
  M. E. Witkowski, K.J. Drozdowski, M. Makowski, W. Drozdowski, A. J. Wojtowicz, K. Irmscher, R. Schewski & Z. Galazka
  
• Methods of Prospecting, Research and Optimization of Scintillator Materials
  W. Drozdowski
  
• Radiation Detectors and Plasma Diagnostics Division Seminar at National Centre for Nuclear Research in Świerk, Poland (on-line), 7 October 2021 "Scintillation Mechanism in β-Ga2O3, the New Semiconducting Scintillator; Can We Improve It?"
  A. J. Wojtowicz
  
• Radiative and Nonradiative Recombination in β-Ga2O3 Scintillator Crystals
  A. J. Wojtowicz, M. E. Witkowski, M. Makowski, W. Drozdowski, K. Irmscher, R. Schewski & Z. Galazka
  
• Recent progress in the development of β-Ga2O3 scintillator crystals grown by the Czochralski method. Optical Materials Express, 11(8), 2488.
  Drozdowski, Winicjusz; Makowski, Michał; Witkowski, Marcin E.; Wojtowicz, Andrzej J.; Irmscher, Klaus; Schewski, Robert & Galazka, Zbigniew
  
• Scintillation Time Profiles of Czochralski-Grown β-Ga2O3 and β-Ga2O3:Si Crystals
  M. Makowski, M. E. Witkowski, A. Bachiri, W. Drozdowski, A. J. Wojtowicz, K. Irmscher, R. Schewski & Z. Galazka
  
• Scintillation Yield of Czochralski-Grown β-Ga2O3 and β-Ga2O3:Si Crystals
  A. Bachiri, M. Makowski, W. Drozdowski, M. E. Witkowski, A. J. Wojtowicz, K. Irmscher, R. Schewski & Z. Galazka
  
• Scintillation Yield of β-Ga2O3 and β-Ga2O3:Si Studied by Pulse Height Technique
  A. Bachiri, M. Makowski, W. Drozdowski, M. E. Witkowski, A. J. Wojtowicz, K. Irmscher, R. Schewski & Z. Galazka
  
• Seminar at Ohio State University, Ohio, USA (on-line), 3 June 2021 “Bulk β-Ga2O3 single crystals – growth by the Czochralski method and physical properties”
  Z. Galazka
  
• Seminar at University of Warsaw, Institute of Physics, Warsaw, Poland (on-line), 15 January 2021 “Ultra-wide bandgap oxide semiconductor β-Ga2O3: bulk single crystals, physical properties, and applications”
  Z. Galazka
  
• Growth of bulk β-Ga2O3 single crystals by the Czochralski method. Journal of Applied Physics, 131(3).
  Galazka, Zbigniew
  
• Heading for brighter and faster β-Ga2O3 scintillator crystals. Optical Materials: X, 15, 100157.
  Drozdowski, Winicjusz; Makowski, Michał; Bachiri, Abdellah; Witkowski, Marcin E.; Wojtowicz, Andrzej J.; Swiderski, Lukasz; Irmscher, Klaus; Schewski, Robert & Galazka, Zbigniew
  
• Low temperature thermoluminescence of β-Ga2O3 scintillator. Optical Materials: X, 16, 100210.
  Witkowski, Marcin E.; Drozdowski, Konrad J.; Makowski, Michał; Drozdowski, Winicjusz; Wojtowicz, Andrzej J.; Irmscher, Klaus; Schewski, Robert & Galazka, Zbigniew