Imaging performance of polycrystalline mercuric iodide films on CMOS readout arrays

Polycrystalline mercuric iodide (HgI2) films have great potential as direct-conversion x-ray detectors for digital x-ray imaging. The basic characteristics of HgI2, such as stopping power, mobility-lifetime product, and mean energy to create an electron-hole pair, are superior to or equivalent with those of other direct converters such as amorphous Se, PbI2, and CZT. Single-crystal HgI2 detectors have demonstrated excellent energy resolution and detection efficiency, and polycrystalline film performance has been approaching that of single crystals over the last few years. We have created high-resolution x-ray imaging devices using polycrystalline films grown directly onto CMOS readout chips using a thermal vapor transport process. The use of CMOS technology allows small pixels, fast readout speeds, and cost-effective devices due to well-developed fabrication processes.