Carrier surface generation and recombination effects in photoconduction of HgI2 single crystals

Abstract

Dc photoconductivity characteristics of HgI₂ single crystals have been measured in the range of 1.75–2.75 eV, using CuI as a transparent electrical contact. Hole and electron photocurrents could be separately measured by applying different voltage polarities to the illuminated electrode. It is shown that charge carrier generation near the surface is highly extrinsic, as displayed by differences in the hole and electron photogeneration spectra. Analysis of the photoconductivity versus voltage characteristics indicates that the hole and electron bulk trapping times satisfy τ_p >70 μs and τ_n >3 μs, respectively. The hole and electron surface recombination velocities were s_p =1.0×10⁴ cm/s and s_n =8×10⁵ cm/s, respectively.