Effect of In additive on the electrical properties of Se–Te alloy
Semiconductor Science and Technology
The electrical properties of Se 80-x Te 20 Bi x (x = 0, 2, 4, 6, 8) amorphous thin films prepared by thermal evaporation technique have been studied. The dark conductivity (σ d ), charge carrier concentration (n σ ) and photoconductivity (σ ph ) increases as the concentration of Bi additive increases upto x = 4 at. % in a-Se 80-x Te 20 Bi x thin films. The activation energy (ΔΕ) and photosensitivity (σ ph /σ d ) decreases sharply after Bi incorporation. As the Bi concentration further increases
... n further increases (when x = 6 at. %) a reverse in the trend has been observed for all these parameters. With further increase of Bi content in Se 80-x Te 20 Bi x amorphous thin films (when x = 8 at. %), the dark conductivity (σ d ), charge carrier concentration (n σ ) and photoconductivity (σ ph ) again increases and activation energy (ΔΕ d ) and photosensitivity (σ ph /σ d ) decreases. Intensity dependence of photoconductivity has also been studied at 303 K and follows a power law as σ ph ∝ F γ , where γ lies between 0.5 and 1. The differential life time (τ d ) is determined from the decay of photocurrent with time. The differential life time increases as the Bi concentration increases upto x = 4 at. % and decreases with further increase of Bi content (when x = 6 at. %) and then again increases as Bi content in Se 80-x Te 20 Bi x amorphous thin films further increases upto x = 8 at. %. The results are explained on the basis of increase in the density of localized states present in the mobility gap of Se 80-x Te 20 Bi x thin films.