Enhancement of Mercuric Iodide Detector Performance Through Increases in Wafer Uniformity by Purification and Crystal Growth in Microgravity
B W. Steiner, L van den Berg, U Laor
Wafers from mercuric iodide crystals grown in microgravity on two occasions have previously been found to be characterized by a higher hole mobility-lifetime produce, which enables energy dispersive radiation detectors with superior resolution. In the present work we have identified the specific structural modifications that are responsible for this enhanced performance. As a result of this study, the performance of terrestrial wafers also has been improved but not yet to the level of wafers grown in microgravity. High resolution synchrotron x-ray diffraction images of a series of wafers including both those grown in microgravity and on the ground revel two principal types of structural changes, which are interrelated. One of these, arrays of inclusions, affects performance far more strongly than the other, variation in lattice orientation. Inclusions can be formed either from residual impurities or in response to deviations from ideal stoichiometry. The formation of both types is facilitated by gravity-driven convection during growth. As the level of inclusions is reduced, through growth from material of higher purity, through the achievement of balanced stoichiometry, or by suppression of convection mixing during crystal growth, the hole mobility-lifetime produce is enhanced in spite of an accompanying decreased uniformity in lattice orientation.
, Van, L.
and Laor, U.
Enhancement of Mercuric Iodide Detector Performance Through Increases in Wafer Uniformity by Purification and Crystal Growth in Microgravity, Journal of Applied Physics
(Accessed December 9, 2023)