Study of trapping levels in α-HgI₂ crystals by UV and isothermal current measurements

UV spectra and isothermal current (I-t curves) measurements have been performed in order to determine the trapping levels in α-HgI₂ crystal grown by a static sublimation method. Four absorption bands, with different absorption intensity, were found at 1572.5, 1729.2, 2117.5 and 2305.8 nm in the UV spectra. According to a simple energy level model, the first two, corresponding to 0.79 0.01 and 0.72 eV, respectively, were confirmed to be the absorption of trapping levels from the I-t data, whereas the last two were not assigned due to insufficient data from the I-t measurements. Our discussions on the characterization of the energy levels suggest that the four absorption bands in the UV spectra may be derived from structural defects in the HgI₂ crystal.