CdZnTe radiation detectors for hard X-ray astronomy
thesisposted on 15.12.2014, 10:40 by Greg. Bale
This thesis is concerned with the development of CdZnTe compound semiconductor detectors for hard X-ray astronomy. The advent of multilayer coated focusing optics for hard X-rays creates the need for compact solid-state X-ray detectors with substantial quantum efficiency above 10 keV. CZT is a material with the necessary properties to meet the requirements.;Excellent results from commercially obtained CdZnTe detectors are presented in Chapter 4 of this work. Low-noise preamplifiers and Peltier coolers were employed to obtain high-resolution X-ray and gamma-ray spectra over the 2 - 60 keV energy range. 55Fe spectra have been acquired with a resolution of <218eV FWHM and peak-to-background ratios in excess of 200:1. Data have been obtained at a range of energies to enable measurements of fundamental properties of the detector and material, including the Fano factor.;A program of modelling was also undertaken and the work is presented in Chapter 3. Using the simulation, the mobility-lifetime products of the CZT material were determined to be ee = (3.9 0.15) x 10-3 cm2V-1 and hh = (1.2 0.2)x 10-5 cm2V-1. A dead-layer is hypothesized to lie beneath the electrodes of the CZT devices and the model was used to parameterize the depth of this region to 500-1000nm. Two-dimensional FITS arrays were also generated to describe the detector response to a range of input energies.;Chapter 5 describes the manufacture and processing of CZT crystals. Spectroscopic crystals were successfully produced, including a novel device geometry. Finally, work intended to form the basis for pixel array development is presented in Chapter 6.