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ARTICLE

Photoelectric Properties of Amorphous Selenium Thin Films Deposited by Thermal Evaporation

Zhadyra Toreniyaz¹, Guzal Ismailova¹, Oleg Prikhodko¹, Zhasulan Nakysbekov¹, Tilek Kuanyshbekov², Nurkadam Tolep¹, Dmitry Terekhov³, Zhandos Tolepov^1,*

1 Department of Physics and Technology, Al-Farabi Kazakh National University, Al-Farabi Avenue, 71, Almaty, Kazakhstan
2 Kaz Graphene Limited Liability Partnership, Western str., 63, Ust-Kamenogorsk, Kazakhstan
3 National Research University of Electronic Technology, Shokina str., 1, Zelenograd, Moscow, Russia

* Corresponding Author: Zhandos Tolepov. Email:

Chalcogenide Letters 2026, 23(5), 1 https://doi.org/10.32604/cl.2026.081101

Received 23 February 2026; Accepted 09 May 2026; Issue published 02 June 2026

Abstract

Amorphous selenium (a-Se) thin films were deposited by vacuum thermal evaporation and investigated in planar photoconductive structures to evaluate their optical and photoelectrical properties in the low-field regime. SEM analysis showed continuous film coverage with a thickness of about 250 nm. Raman spectroscopy and X-ray diffraction confirmed the amorphous structure of the as-deposited films and the formation of trigonal crystalline selenium after annealing. Optical analysis based on transmission and reflectance spectra yielded an optical band gap E g = 1.96   eV and an Urbach energy E U = 0.083   eV , indicating localized tail states associated with structural disorder. The planar devices exhibited nearly linear and symmetric dark current-voltage characteristics within V ≤ 10   V , corresponding to an electric field range of 100–1000 V/cm. Under illumination at λ = 633   nm , the photocurrent showed a sublinear dependence on incident light power density, I photo ∝ P λ γ , with γ = 0.55 . The responsivity increased with the electric field, which indicates more efficient collection of photogenerated carriers at higher bias. Temperature-dependent measurements over the range 303–343 K showed that both the dark current and the current under illumination increase with temperature, whereas the relative photoresponse decreases because the dark current increases more rapidly. Arrhenius analysis yielded effective activation energies 0.836 eV for the dark current and 0.709 eV for the current under illumination. These results show that the optical disorder parameters and the photoelectrical response are mutually consistent. In weak electric fields, the behavior of planar a-Se films is governed by competition between thermally activated dark conduction and field-assisted collection of photogenerated carriers.

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