Properties of electrodes on HgI2 polycrystalline films

In the present work we report, for the first time, on the contact properties of detectors made with polycrystalline α-HgI2 films. α-HgI2 films were grown by the physical vapor deposition (PVD) method onto floating glass substrates coated with different metals (Pd, Zn etc.), carbon (aquadag (Aq)) and ITO (indium tin oxide), which will act as rear contact. Detectors were then assembled on the as-grown films, depositing as front contact the same material as of the rear one, for Pd and carbon electrodes, and using Pd as front electrode for films grown onto ITO-coated substrates. In addition, Aq was also used as front contact when Pd was the rear one. Electrodes with and without guard ring were made to evaluate surface leakage currents and the guard ring was then used for the following characterization. Electrical properties were measured giving resistivities in the order of 1012 Ω cm at room temperature and the results for different electrode materials were compared. Barrier contact heights of about 1.0 eV and their lowerings (up to 0.07 eV at 90 V) were determined for detectors made with ITO, Pd and Aq. Results were compared with the ones previously reported for detectors made with α-HgI2 single crystals.