Photoconductivity and Electrical Properties of Pb1 - xSnxTe thin films

PbSnTe can be used in the fabrication of IR photoresistors and IR photodiodes. PbSnTe films are economic, if compared with bulk materials. Due to the importance of this material, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$ Pb_{1 - x} Sn_x Te $$ \end{document} thin films were prepared with x=0.0, 0.1, 0.2, 0.3 and 0.4 by a flash evaporation technique. The interplanar spacing d, and consequently the reflecting planes (h k l) were identified, from the powder X-ray diffraction analysis. The as-deposited thin films of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$ Pb_{1 - x} Sn_x Te $$ \end{document} were polycrystalline. As tin substitutes for lead in the prepared films, the interplanar spacing d decreases and the unit cell dimension a also decreases. Energy dispersive X-ray analysis (EDX) was carried out. From the composition of these films determined by EDX excess Te was detected for x=0.0 and 0.1, while a slight Te deficiency was observed for x=0.2, 0.3 and 0.4. Besides a slight Sn deficiency was found for films of x=0.1, 0.3 and 0.4. On the other hand a slight excess of Sn was present for x=0.2. The electrical properties, example, the electrical resistivity, the Hall coefficient and Hall mobility, were studied in the temperature range 100–450 K. The electrical transport properties of the investigated films are governed by scattering mechanisms, associated with the intergrain barrier height. A.c. photoconductivity measurements were carried out by using the frequency-dependence method. The carrier lifetime was determined for all the investigated films at temperatures of 100, 200, 300 and 400 K. This ranged from 12–20 ms at 100 K. The steady-state photoconductivity, photoconductivity, photosensitivity and the carrier lifetime were studied in the temperature range 100–450 K. The photosensitivity increases sharply at a temperature ∼100 K. Combining the results of the photoconductivity and the electrical measurements, it appears that x=0.1 is a suitable composition for further study to prepare IR device, since it has the best photosensitivity and good electrical properties.