Photoconductivity inKTaO3:Li single crystals

Abstract

Photoconductive currents of the same order of magnitude as in conventional impurity-doped semiconductors have been observed at temperatures lower than 80 K in the ${\mathrm{K}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Li}}_{\mathit{x}}$ ${\mathrm{TaO}}_3$ (KTL) mixed system (with 0.016≤x≤0.05) and under light illumination with energy lower than the band gap. The dependence of the photoconductivity on temperature, Li concentration, and external electric field as well as on sample history and treatment is studied. The results are interpreted and discussed on the basis of a model allowing a calculation of the impurity levels taking into account the displacement of the oxygen ions nearest to the off-center position of the ${\mathrm{Li}}^{+}$.