Comparison of the Optical and Electrical Properties of Al-Doped ZnO Films Using a Lorentz Model

Jin-Cherng Hsu,Yu-Yun Chen

doi:10.3390/coatings9010004

Abstract

In this research, zinc oxide (ZnO) films are doped with various amounts of Al dopants, from 0 to 13 at.%, using ion-beam co-sputtering for Zn and Al metallic targets at room temperature. The Al-doped ZnO (AZO) films appear to have lower transmittances in the UV and near-IR ranges. The electrical and optical properties of each film are successfully analyzed by using the spectroscopic ellipsometry of two Lorentz oscillators for the two lower transmittances. The optimal AZO film is deposited with an Al-dopant of 1.5 at.% at an oxygen partial pressure of 0.12 mTorr; it has the smallest resistivity of 7.8 × 10−4 Ω cm and high transmittance of > 80% in the visible regions. The free carrier concentration and mobility evaluated using ellipsometry are different from those measured using the Hall effect. This phenomenon was the result of the grain boundary scattering due to the small ~20-nm grain size of the AZO film used in this study.

Highlights

Conductive transparent oxide (CTO) films have high transmittance in the visible light region and high reflectance in the IR region in combination with a high conductivity; they are widely used in electronic and optical devices
Al-doped Zinc oxide (ZnO) (AZO) film has played a significant role in the development of optoelectronic devices [8,9,10,11]
92.6 ± 28.1 nm using ion-beam sputter deposition (IBSD) at room temperature under different oxygen partial pressure (PO2 )

Summary

Introduction

Conductive transparent oxide (CTO) films have high transmittance in the visible light region and high reflectance in the IR region in combination with a high conductivity; they are widely used in electronic and optical devices. Zinc oxide (ZnO) film, a CTO film, has a hexagonal wurtzite structure [1] It is an n-type semiconductor and has a direct wide bandgap of approximately. Al-doped ZnO (AZO) film has played a significant role in the development of optoelectronic devices [8,9,10,11]. It is highly visible transparent and has metal-like electrical conductivity [1]. Spectroscopic ellipsometry is one of the methods used to determine the thickness, surface roughness, and optical constants using various dispersion models [12,13,14]

Methods

Results

Conclusion