Optical and Dispersion Parameters of the Al-doped ZnO Thin Film

Authors A.I. Kashuba1 , B. Andriyevsky2 , H.A. Ilchuk1 , R.Yu. Petrus1 , T.S. Malyi3, I.V. Semkiv1

1Lviv Polytechnic National University, 12, S. Bandera St., 79646 Lviv, Ukraine

2Faculty of Electronics and Computer Sciences, Koszalin University of Technology, 75-453 Koszalin, Poland

3Ivan Franko National University of Lviv, 8, Kyrylo and Mefodiy St., 79005 Lviv, Ukraine

Е-mail ashuba07@gmail.com
Issue Volume 13, Year 2021, Number 4
Dates Received 09 March 2021; revised manuscript received 06 August 2021; published online 20 August 2021
Citation A.I. Kashuba, B. Andriyevsky, H.A. Ilchuk, et al., J. Nano- Electron. Phys. 13 No 4, 04006 (2021)
DOI https://doi.org/10.21272/jnep.13(4).04006
PACS Number(s) 78.20. − e, 78.20.Ci, 78.55.Et
Keywords Thin films (60) , Absorption (17) , Dispersion (19) , Refractive index (3) , Transmission (16) , Optical function, Relaxation time. .

The results of studies of the dispersion of optical functions and optical constants for zinc oxide thin film doped with aluminum are presented. The deposition of Al-doped ZnO (2.5 wt. %) thin films is performed by magnetron sputtering. Al-doped ZnO thin film crystallizes in a hexagonal structure (structure type ZnO, space group P63mc (No. 186) with unit-cell dimensions a  3.226(2) Å and c  5.155(6) Å (V 46.49(6) Å3). Optical transmittance spectra (300-2500 nm) shows that the Al-doped ZnO thin film is of high optical quality, and the value of the optical band gap (3.26 eV) is very close to undoped samples. The study of optical functions is performed on the basis of the experimentally measured transmission spectrum using the bypass method. The spectral behavior of optical functions, such as refractive index, extinction coefficient, absorption index, dielectric functions and optical conductivity, is established. The value of Urbach energy and the dependence of oscillator strength on the size of the band gap and the concentration of doping element are determined. It is observed an increase in Urbach energy for the Al-doped ZnO thin film in comparison to the undoped ones. An almost twofold increase in the optical oscillator strength value is revealed for the thin film studied. The influence of aluminum doping on the dynamic change of optical mobility, optical resistance and relaxation time is established for the first time for the studied compound. The value of the plasma frequency is also determined and its correlation with the carrier density is defined. The doping of ZnO thin films with aluminum leads to an increase in optical mobility, relaxation time and plasma frequency that is revealed by comparison with reference data for the undoped ZnO. Due to good optical properties, this thin film is a good candidate as a material for optoelectronic devices.

List of References