Dark current transients in HgI2 single crystals used as γ- and x-ray spectrometers

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Abstract
Transient characteristics of dark currents have been measured in HgI2 single crystals as functions of voltage and temperature. The existence of a hole trapping center, 0.7 eV deep and of density ∼1015 cm−3, was established, which effectively lowers the hole drift mobility by about seven orders of magnitude. The samples were found to be slightly extrinsic n type, the Fermi level being 0.9 eV deep. The room‐temperature electron density was about 2×103 cm−3. The meaning of these characteristics to the performances of HgI2 γ‐ and x‐ray spectrometers is discussed. Particularly, it is suggested that lowering of the HgI2 detector operation temperature to about 0 °C will improve its energy resolution capabilities.