Picture of Open Access badges

Discover Open Access research at Strathprints

It's International Open Access Week, 24-30 October 2016. This year's theme is "Open in Action" and is all about taking meaningful steps towards opening up research and scholarship. The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs. Explore recent world leading Open Access research content by University of Strathclyde researchers and see how Strathclyde researchers are committing to putting "Open in Action".


Image: h_pampel, CC-BY

Development of low-pressure vapour-phase epitaxial GaAs for medical imaging

Bates, RL and Manolopoulos, S and Mathieson, K and Meikle, A and O'Shea, V and Raine, C and Smith, KM and Watt, J and Whitehill, C and Pospisil, S and Wilhelm, I and Dolezal, Z and Juergensen, H and Heuken, M (1999) Development of low-pressure vapour-phase epitaxial GaAs for medical imaging. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 434 (1). pp. 1-13. ISSN 0168-9002

Full text not available in this repository. (Request a copy from the Strathclyde author)


A summary is given of progress accomplished with the development of low-pressure vapour-phase epitaxial GaAs as a material for X-ray detectors. As the III–V concentration ratio is altered from Ga-rich to As-rich, the material is shown to improve from p-type, to n-type with compensation via deep levels, to n-type with a doping density of 1.7×1014 atoms cm−3. The measured barrier height is 0.8 V, as expected for the Ti contact used. Overdepletion was obtained before breakdown, enabling a layer thickness of m to be deduced for the final sample. For the later samples, charge collection for 60 keV Am-241 gammas was bias independent at a value of 100±8%. Spectra were also obtained from Sr-90 electrons. The most probable value of the charge collected as a function of the bias reached a plateau and from this value a depletion width of m was found for the final sample, equal to the epitaxial layer thickness. Results from detailed alpha and low-energy proton spectroscopy are shown for diodes fabricated from this material. A charge collection efficiency of 100% was obtained when the diode could be depleted sufficiently. The concept of a charge collection depth was introduced, since a significant amount of charge was collected without bias. The minimum depth of such a region was shown to be m at 0 V reverse bias, far greater than the m predicted for the depletion depth. Charge coupling between the guard ring and the pad was observed and successfully modelled.