Characteristics of Quaternary Flexible Mg and Ga Co-Doped ZnO Thin Films Fabricated Using RF Magnetron Sputtering

Mg and Ga co-doped ZnO (MGZO) thin films with transparent conductive characteristics and low resistivity have been fabricated using a radio frequency (RF) magnetron sputtering process. Doped ZnO thin films with 0.5 at.% Mg and 0.3 at.% Ga were grown based on our previous investigation on polyethylene terephthalate substrates (PET) using different sputtering powers from 50 to 150 W. The influence of the various sputtering powers on the structural, morphological, compositional, optical and electrical properties of the MGZO thin films were investigated. X-ray diffraction patterns show that all of the films had a hexagonal wurtzite ZnO structure with a c-axis preferential growth. The MGZO thin films had directional uniform morphologies. The optical properties of the MGZO thin films demonstrated a high transmittance of approximately 80% and a band gap energy of 3.58 eV. The resistivity, the mobility and the carrier concentration of the MGZO thin films varied gradually from 2.4 × 10^–2 to 3.7 × 10^–3 Ωcm, 1.23 to 5.0 cm²/Vs and 1.91 × 10^–20 to 2.51 × 10^–20/cm³, respectively, with an increase in the sputtering power.