Effect of Sn addition on the photoconductivity of narrow-gap Sb₂Se₃ films

Abstract

Steady state and transient photocurrent measurements have been performed on thermally evaporated Sb₂Se₃:Sn films. The DC conductivity increases accompanied by a decrease in the DC activation energy and the pre-exponential factor with increasing Sn content. A red shift in the reflectivity maxima was observed with an increase in Sn concentration. Sn addition inhibits photodegradation with a decrease in the photosensitivity. The transient decay process fits well to a stretched exponential function. Values of fit parameters, decay time constant, and the dispersion parameter are reported for the Sb₂Se₃:Sn system. Bimolecular recombination is predominant for the Sb₂Se₃ films, while it changes towards a monomolecular process with increase in the Sn content. An increase in the density of hole trapping centers with the inclusion of Sn as a charged entity is proposed to explain the results.

Keywords:

• amorphous semiconductors
• thin films
• electrical properties

Acknowledgements

P. Kumar gratefully acknowledges the financial support as SRF (Extended) from the CSIR, New Delhi [No. C9/254 (0171)/2008-EMR-1]. The authors wish to thank Dr T.S. Sathiaraj, Department of Physics, University of Botswana for his kind cooperation in making the reflectivity measurements, EDAX, and thickness measurements. The authors are also thankful to Mr Jagtar Singh (Technician), Regional Sophisticated Instrumentation Facility, Punjab University, Chandigarh for his help in obtaining the XRD patterns.