PHOTOINDUCED ELECTRONIC TRANSPORT IN K1-XLIXTAO3

Photocurrent and Hall effect measurements were performed on K0.984Li0. 016TaO3 and K0.966Li0.034TaO3 single crystals under illumination with 514.5-nm and UV Light. The currents observed are carried by electrons, whose mobility does not undergo large variations on cooling across th e dipole-glass freezing temperature T-f. The sharp increase of photocu rrent occurring in the polar phase is primarily due to enhancement of carrier density. The effect is much larger after field cooling, being accompanied in this case by persistent currents. The present results l ead us to conclude that hole traps with vanishing cross section for el ectron recombination are active below T-f.