Development of mercuric iodide nuclear detectors in our laboratory has concentrated on crystalline perfection, optimization of electronic properties, and device fabrication. Increased crystalline perfection can be obtained with better crystal growth temperature control combined with slightly modified growth parameters. Adjustment of the stoichiometry of the crystal growth source material has increased the mobility-trapping time (..mu.. tau) product for the holes. Preliminary experiments with different contact materials and contacting techniques gave ambivalent results.