Abstract
Spectral dependency and electric field dependency of photoconductivity of purified TlCl have been studied at low temperatures, mostly at 17°K and 81°K, by the standard transient method with blocking electrodes and using exciting light of low intensity. When traps in the crystal are empty, higher photoresponses under hole polarity than those under electron polarity have been observed at 17°K and vice versa at 81°K, indicating that the photoconductivity is of two-carrier. The results are analyzed from the standpoint of two-carrier and low field unit ranges of electrons and holes are determined. With these unit ranges, schubwegs of electrons and of holes are estimated as functions of electric field from the field dependence of photoconductivities under both polarities. They obey Ohm’s law at 81°K but are proportional to E0.5 above certain critical fields at 17°K. Low field unit range of holes has been found to be larger than that of electrons below 50°K and smaller above this temperature. Effect of filling traps to unit ranges and a contribution of surface layer to photoresponse have been investigated. Electrical glow peaks have been observed at 63°K and 85°K.
