Feasibility of HgBrI as photoconductor for direct X-ray imaging

Films of HgBrI (eutectic composition) were grown by the physical vapor deposition method on palladium-coated glass substrates 2"times2" in size. The growth was performed in a system especially designed and constructed for getting a fine control of the growth parameters. The best growth conditions were a source temperature of 116degC, a growth temperature of 50degC and a growth time of 3 hours, with an initial pressure of 6times10^-3 Pa. Film thicknesses and grain sizes gave values ranging between 100 and 350 mum (10%), and between 10 and 50 mum, respectively. The dark current density of the films is higher than 10 pA/mm² for electric fields above 0.03 V/mum, and the resistivity is 3.8times10¹¹ Omegacm. An electron mobility-lifetime of 6times10^-6 cm^2/2V was estimated. HgBrI films give a sensitivity to X-rays of 65 nC/Rcm² , and a signal to dark relation of 12 at 750 mR/s and 32 KVp, with an electric field of 0.9 V/mum applied to the film. Dark current density, resistivity, electron mobility-lifetime product and response to the X-ray of the films are acceptable taking into account that this is the first attempt on growing films with this material, and indicate HgBrI as a new compound semiconductor candidate for the application