Tunneling recombination processes in PbWO₄ crystals

Abstract

Time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 160-300 K for undoped and Mo-doped PbWO 4 crystals under XeCl (4.02 eV), N 2 (3.67 eV) and KrF (5.0 eV) pulsed excimer laser excitation. The G(II) emission was found to be responsible for the slow (µs-ms) luminescence decay. Under excitation or after irradiation in the exciton region (E exc = 4.02 eV), this emission accompanies the monomolecular tunneling recombination in genetic pairs of electron and hole centers produced at the photo-thermally stimulated decay of localized excitons, which occurs without release of free charge carriers. Under excitation or after irradiation in the host lattice (E exc = 5.0 eV) and defectrelated (E exc = 3.67 eV) regions, the bimolecular tunneling recombination takes place in chaotic pairs of the electron and hole centers created at the trapping of optically released free charge carriers.

Tunneling recombination luminescence under excitation of PbWO4:Mo crystals in the defect-related absorption region

“…Such decay kinetics of the G(II) luminescence was observed in Ref. [12] under excitation of PbWO 4 crystals in the localized exciton related absorption region.…”

“…Besides the fast decay, slow processes were observed at room temperature (RT) (see, e.g., Refs. [10][11][12]). In Ref.…”

“…[4][5][6][7][8][9][10][11][12]. Besides the fast decay, slow processes were observed at room temperature (RT) (see, e.g., Refs.…”

“…In Ref. [12], it was shown that only the G(II) emission is responsible for the slow part of the green luminescence decay. The study of the luminescence decay kinetics carried out in Ref.…”

“…The study of the luminescence decay kinetics carried out in Ref. [12] under excitation in the localized exciton absorption region (around 4.0-4.1 eV) showed that the decay curve can be approximated by the formula I(t)$t Àa where a is independent both of the temperature and of the excitation intensity. At low excitation intensities, the dependence of the emission intensity on the excitation intensity was found to be linear.…”