pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2020; 70: 524-530

Published online June 30, 2020 https://doi.org/10.3938/NPSM.70.524

## Spectroscopic Characteristics of Zn$_{1-x}$Mn$_{x}$S Thin Films by Ellipsometry and Absorptance Measurements

Dae Jung KIM1, Bong Jin KIM1, Duk Hyeon KIM1, Jong Won LEE2*

1School of Basic Sciences, Hanbat University, Daejeon 34158, Korea

2Department of Advanced Materials Engineering, Hanbat University, Daejeon 34158, Korea

Correspondence to:jwlee@hanbat.ac.kr

Received: March 16, 2020; Revised: April 6, 2020; Accepted: May 11, 2020

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

### Abstract

Zn$_{1-x}$Mn$_{x}$S thin films were grown on GaAs(100) substrates by using hot-wall epitaxy. X-ray diffraction patterns revealed the crystal structure of the epilayer. The optical properties were investigated using spectroscopic ellipsometry at 300 K from 3.0 -- 8.7 eV. The obtained data were analyzed to determine the critical points of the pseudodielectric function spectra, $\langle\varepsilon(E)\rangle=\langle\varepsilon_{1}(E)\rangle+\langle\varepsilon_{2}(E)\rangle$, such as $E_{0}/E_{0}+\Delta_{0}$, $E_{1}$, and three $E_{2}(\Sigma,\Delta,\Gamma)$structures. These critical points were determined by fitting analytical line-shapes to numerically calculated derivatives of the pseudodielectric functions. In particular, the transmittance/absorptance measurements were carried out to obtain the optical properties of the Zn$_{1-x}$Mn$_{x}$S epilayers, and the exact optical energy bandgap ($E_{g}$) was determined by comparing these results with the results of the ellipsometry measurements. Also, the energy band structures from the ellipsometry and the absorptance measurements were analyzed as a function of Mn concentration. The results obtained demonstrate that ellipsometry can be efficiently and non-destructively used to examine the energy bandgap of Zn$_{1-x}$Mn$_{x}$S epilayers.

Keywords: Zn$_{1-x}$Mn$_{x}$S thin film, Spectroscopic ellipsometry, Hot-wall epitaxy, X-ray diffraction patterns, Pseudo dielectric functions, Critical points, Transmission measurement