Imaging performance of polycrystalline mercuric iodide films on CMOS readout arrays

Polycrystalline mercuric iodide (HgI
2
) films have great potential as direct-conversion x-ray detectors for digital x-ray imaging. The basic characteristics of HgI
2
, 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, PbI
2
, and CZT. Single-crystal HgI
2
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.