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 40degC and a growth time of 3 h, with an initial pressure of 6times10^-3 Pa. Film thicknesses and grain sizes gave values ranging between 100 and 350 mum (10%), and between (10plusmn5) and (50plusmn20) mum, respectively. The dark current density of the films is higher than 10 pA/mm² (maximum value required for the application) for electric fields above 0.03 V/mum, and the resistivity is 3.8times10¹¹ Omega.cm. Electron and hole mobility-lifetimes of 7.1times10^-6 cm²/V y 1.0times10^-5 cm²/V were estimated. HgBrI films give a sensitivity to X-rays of 65 nC/Rmiddotcm² for an X-ray beam of 70 KVp, with an electric field of 0.25 V/mum applied to the film. Taking into account that this is the first attempt on growing films with this material, these results indicate HgBrI as a new compound semiconductor candidate for the application