Tailoring the Structural and Optoelectronic Properties of Al-Doped Nanocrystalline ZnO Thin Films

Abstract

This paper describes the effect of Al doping (0 at.% to 6 at.%) on the structural and optoelectronic properties of nanocrystalline ZnO thin films deposited by thermal evaporation. X-ray diffraction patterns confirm that an increase in Al concentration (from 0% to 6%) in ZnO lowers the crystallinity of the films and reduces grain size. Al doping is also found to influence the optical properties of the ZnO thin films. Visible transmittance above 85% was obtained by increasing the Al doping to 6%. The optical bandgap was found to vary from 3.20 eV to 3.97 eV with changing Al content from 0% to 6%, which is in accordance with the Burstein-Moss shift. The mobility of ZnO thin films can be varied from 5.60 cm 2 /Vs to 24.25 cm 2 /Vs, the carrier concentration from 5.93 9 10 18 /cm 3 to 9.11 9 10 20 /cm 3 , and the resistivity from 4.62 9 10 À4 X cm to 4.34 9 10 À2 X cm, depending on the Al doping concentration (0% to 6%). This study suggests that ZnO:Al films can be tailor-made to meet the requirements for various optoelectronic applications such as flexible photocells or ultraviolet (UV) photodetectors covering a wide range of short wavelengths.

Comparative Study of As-Deposited ZnO Thin Films by Thermal Evaporation, Pulsed Laser Deposition and RF Sputtering Methods for Electronic and Optoelectronic Applications

“…These properties of ZnO thin films depend on the deposition techniques, deposition parameters, doping and post-deposition treatments of the films. [8][9][10][11][12] Although all these factors improve the quality of the films they are at the cost of extra energy, time and resources. High-quality ZnO thin films can be deposited by various techniques like radio-frequency (RF) sputtering, the sol-gel method, thermal oxidation of metallic zinc, thermal evaporation of ZnO powder, 12,13 pulsed laser deposition (PLD) 14 and spray pyrolysis.…”

Simulation, Fabrication and Characterization of ZnO Based Thin Film Transistors Grown by Radio Frequency Magnetron Sputtering

“…The sheet resistance (R sh was measured by using a four-point probe setup. The resistivity was calculated from the sheet resistivity of the thin-film layer by using the following relationship 40 = R sh × t…”

Effects of Rapid Thermal Annealing on Electrical Transport in Heavily Doped ZnO Thin Films Deposited at Different Substrate Temperatures

“…1 At present, both pure and impurity-doped ZnO thin films, e.g., Al-doped ZnO (AZO) and Ga-doped ZnO (GZO), have been widely studied because of the advantages of low cost, non-toxicity, and stability in hydrogen plasma. [2][3][4] High-quality ZnObased thin films feature a decrease in both optical absorption in the near-infrared range and electrical resistivity, which are of great importance to enhance solar cell efficiency. 5 The low optical absorption and electrical resistivity can be achieved by increasing the carrier mobility rather than the free carrier concentration due to the plasmonic absorption when a high transmittance in the NIR spectral region is required.…”