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''/spl times/2'' 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 116/spl deg/C, a growth temperature of 40/spl deg/C and a growth time of 3 h, with an initial pressure of 6/spl times/10/sup -3/ Pa. Film thicknesses and grain sizes gave values ranging between 100 and 350 /spl mu/m (10%), and between (10/spl plusmn/5) and (50/spl plusmn/20) /spl mu/m, respectively. The dark current density of the films is higher than 10 pA/mm/sup 2/ (maximum value required for the application) for electric fields above 0.03 V//spl mu/m, and the resistivity is 3.8/spl times/10/sup 11/ /spl Omega/.cm. Electron and hole mobility-lifetimes of 7.1/spl times/10/sup -6/ cm/sup 2//V y 1.0/spl times/10/sup -5/ cm/sup 2//V were estimated. HgBrI films give a sensitivity to X-rays of 65 nC/R/spl middot/cm/sup 2/ for an X-ray beam of 70 KVp, with an electric field of 0.25 V//spl mu/m 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.