Radiation Detectors and Photodetectors Using Thallium Bromide (TlBr) Crystals

Abstract

  A compound semiconductor, thallium bromide (TlBr), has been investigated as a radiation detector and photodetector material for use in X- and γ-ray spectroscopy. Single crystals of TlBr have been grown by the traveling molten zone method using zone-purified materials. The TlBr crystals have exhibited large mobility-lifetime products of 1-2 × 10^-4 cm²/V and 4-9 × 10^-5 cm²/V for electrons and holes, respectively. X- and γ-ray detectors have been fabricated from the TlBr crystals. An energy resolution of 30 keV FWHM has been recorded for 511 keV γ-rays with the TlBr detector at room temperature. Photodetectors for scintillation spectroscopy have been fabricated from the TlBr crystals by depositing a thin film of Au as an optically transparent electrode on the surface. Quantum efficiency of the TlBr photodetectors has been high in wavelength region below ～460 nm where scintillation emissions of LSO and GSO occur. The TlBr photodetector coupled to an LSO scintillator has exhibited an energy resolution of 34.5% for 511 keV γ-rays.