On the development of compound semiconductor thallium bromide detectors for astrophysics

We discuss the detector requirements for future X-ray astrophysics missions and present preliminary results from our compound semiconductor program designed to produce X-ray detectors with high spatial and spectral resolution across the energy range of 1–200 keV. Several prototype detectors have been fabricated from monocrystalline TlBr and tested at hard X-ray wavelengths in our laboratories and at the ESRF synchrotron research facility. Energy resolutions of 1.6 keV (FWHM) at 5.9 keV and 2.6 keV (FWHM) at 26 keV have been achieved, although we find that performance is highly variable due to polarisation effects. The resolution function is dominated by high leakage current at all energies. From pulse-height measurements of 241Am as a function of detector bias, we derive the electron mobility–lifetime product at −2°C to be (2.9±0.2)×10−4 cm2 V−1. This is about an order of magnitude higher than previously reported values.