Pulse Photoconductivity of Additively Colored KBr

Abstract

The space charge effect in the measurement of a photocurrent of additively colored KBr was investigated by using the repeated pulsive illumination and applying the d.c, and a.c. electric fields. The space charge polarization may arise from the accumulation of the electrons trapped in the surface states, the depth of which is about 0.3 ev. The condition for the absence of space charge was ascertained to be realized by adopting the a.c. field and the pulsive illumination synchronized with plus and minus peaks of the a.c. field. The temperature-dependence of pulse photocurrent was measured by varying the duration of the pulsive illumination. The time constants of current-decay after switching-off of illumination were also observed. Three kinds of electron-traps were found, the one corresponding to F center and the other two to the unknown centers. The activation energies for releasing the electrons trapped in these centers were estimated to be 0.44, 0.35 and 0.43 ev respectively. The growth and bleaching of ...