Excitation and Fe concentration dependences in the impulse photoconductance of InP:Fe

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Abstract
We report impulse response measurements on InP:Fe photoconductors excited by laser and electron beam radiation. Measurements are reported on crystals with Fe concentrations from 2×1015 cm−3 to 4×1016 cm−3 and with excited electron-hole-pair densities of ∼1012 cm−3 and 9×1017 cm−3. Measured signal decays are purely exponential in character, and decay times are inversely related to Fe concentration. No long-lived tails are observed. Decay times show no dependence on excitation level for excited carrier concentrations that are well above and well below the Fe concentrations. The magnitude of the photoresponse indicates that electrons and not holes are the primary current carriers. The data suggest that for impulse excitation photoconductance decay in InP:Fe is due to trap-assisted recombination of electrons and holes at the Fe sites, with a rate determined by the species with the slower capture rate.