Preliminary results on the growth of mercuric iodide epitaxial crystals for use as radiation detectors

In its application as a radiation detector, mercuric iodide shares a common challenge amongst a number of competing semiconductor materials - all have been historically too expensive to grow and fabricate devices to be viable in the larger commercial market. Constellation Technology Corporation has developed a process for the growth of mercuric iodide homoepitaxy. Epitaxial layers with dimensions of 20 mm × 20 mm and a thickness of up to 9 mm have been grown. These layers have been fabricated into both x-ray and gamma ray planar detectors and results have been obtained on 121 pixel (11×11) pixelated detectors. A typical ampoule-grown crystal takes up to 3 months to grow, whereas detector-size layers have been grown with the epitaxial process in just a few days. Additionally, the bulk of the epitaxial growth is in the form-factor of the final, fabricated detector. Therefore, production time and material waste (hence cost) are substantially reduced. Improvements in the mercuric iodide growth process employing epitaxial methods will be described and the results discussed in this paper.