Radio Frequency Sputter Deposition of Ga and F Co-Doped ZnO Thin Films: Effects of Substrate Temperature

Abstract

Doped zinc oxide (ZnO) thin films can be used as transparent conducting electrodes for various optoelectronic device such as flat panel displays andphotovoltaic cells. The present study investigates the effect of substrate temperature on Ga and F co-doped ZnO (GFZO) thin films.The GFZO thin films were deposited on glass substrates by RF magnetron sputtering in CF4/Ar atmosphere with a ZnO:Ga2O3 (3 wt%) target. The structural, electrical, and optical properties of the samples have been observed and analyzed by x-ray diffraction, field emissionscanning electron microscopy, Hall measurements, and UV-visible spectrophotometry. All the GFZO thin films showed the highly c-axis-oriented phase and their average visible transmittances were over 91%. The electrical resistivity of the samples significantly decreased by an order of magnitude to 6.47×10−4Ω-cm as the substrate temperature raised from room temperature to 200 °C. The maximum carrier concentration of 6.10×1020 cm-3 and Hall mobility of 15.4 cm2/V-s were obtained at the optimum substrate temperature at 200 °C. The optical bandgap of the GFZO films has been widened from 3.388 to 3.620 eV with the increase of the substrate temperature. The findings show the developed GFZO thin filmprepared at the higher substrate temperature haveeffectively improved optoelectronic properties andare potentially able to applications in variousoptoelectronic devices.