Impact of Argon Flow Rate on Electrical and Optical Properties of Al-doped ZnO Thin Films with Insight into Ti/Al Ohmic Behaviors to n-ZnO

Abstract

This study explores the impact of Ar flow rate on the electrical and optical properties of Al-doped ZnO thin films and the performance of Ti/Al Ohmic contacts to n-ZnO films. Al-doped ZnO thin films were deposited on glass substrates using a tri-axis RF sputtering system under varying Ar flow rates (30–80 sccm). Electrical properties, including resistivity, carrier concentration, and mobility, were evaluated using Hall measurements, while optical transmittance was analyzed through UV-visible spectroscopy. The resistivity decreased with increasing Ar flow rate, achieving a minimum of 9.74×10−4 Ω⋅cm at 80 sccm, alongside improved mobility and carrier concentration due to enhanced film morphology and crystallinity. We have obtained that the optical transmittance values are between 75% and 80% and we know this as a blue shift phenomenon that occurs at the UV absorption edge due to the Burstein-Moss effect. It is seen that there is an almost ideal behavior in the Ti/Al Ohmic contact, with a specific contact resistivity as low as 1.8×10−5 Ω⋅cm2 in 15 nm Ti layers. We can conclude the importance of optimizing sputtering parameters on film properties for solar cell and optoelectronic device applications. Thus, we conclude that there is an interaction between deposition conditions and material performance to improve electrical conductivity and high transparency in Al-doped ZnO films.