Electrical and photoelectrical properties of vacuum deposited Se-Te-Pb thin films

• Published in: Journal of Optoelectronics and Advanced Materials 2006-04, Vol.8 (2), p.794-799
• Main Authors: Kushwaha, N, Shukla, R K, Kumar, A
• Format: Article
• Language: English
• ISSN: 1454-4164

The d. c. electrical properties of amorphous thin films of Se85Te15-X Pb, prepared by vacuum deposition technique, have been studied at low and at relatively high temperatures. The dark conductivity studies show that the conductivity increases with increasing temperature at all temperature range. Two types of conduction mechanisms were found to dominate in the measured temperature range, namely band conduction through extended states (which dominates at the intermediatetemperature region) and hopping around the Fermi level (which dominates at the low-temperature region). At low temperature, the density of states and other related Mott's parameters are calculated near the Fermi level. A discontinuity, found in the curve at high temperature may be explained due to structural changes that occur near glass transition temperature. Transient photoconductivity measurements at different temperatures and intensities indicate that the decay of photoconductivity is quite slow. Thin films exhibit long-lived residual photoconductivity, called persistent photoconductivity, with an extremely slow decay rate. The persistent photoconductivity increases with an increase in intensity. Photoconductivity decay, even after subtraction of persistent photoconductivity, is found to be non - exponential suggest the presence of continuously distributed deep localised gap states in this material. Differential lifetime and carrier lifetime are also calculated.