Near single-crystal electrical properties of polycrystalline HgI2 produced by physical vapor deposition

Polycrystalline films of HgI₂ prepared by physical vapor deposition (PVD) were found to have electrical charge transport properties similar to those of single crystals. Transient charge transport (TCT) measurements were used to evaluate the electrical conduction properties of the samples. The mobility μ, trapping time τ, and surface recombination velocity s of electrons or holes were determined by analyses of transient voltages developed across the sample in response to a drift of the corresponding charge carriers created by alpha particle absorption near one of the electrodes. Typical electron and hole mobilities were μ_n=88 cm²/V·s and μ_p=4.1 cm²/V·s, respectively; trapping times were τ_n>16 μs and τ_p<3.5 μs, and surface recombination velocities s_n≅1.4×10⁵ cm/s and s_p≅3.7×10³ cm/s. All parameters depend to a large extent on the material deposition technology. The effect of carriers being first generated in near-surface traps and then gradually released is observed.