Effect of deposition distance and temperature on electrical, optical and structural properties of radio-frequency magnetron-sputtered gallium-doped zinc oxide

Abstract Films of gallium-doped zinc oxide (GZO) were deposited on glass substrates by radio-frequency magnetron sputtering using a ceramic target of Ga:ZnO (4 at.% Ga vs. Zn). Both the substrate temperature ( T s ) and the target–substrate distance ( d ts ) were varied and the effect on electrical, optical and structural properties of the resulting films were measured. The highest conductivity of 3200 S/cm was obtained at a deposition temperature of 250 °C, at a d ts of 51 mm. This sample had the highest carrier concentration in this study, 9.6 × 10 20 /cm 3 . Optical transmittance of all films was d ts = 51 mm was smaller than the grain size for films grown with a shorter d ts ; moreover, the films with d ts = 51 mm exhibited the smoothest surface, with a root mean square surface roughness of 2.7 nm. Changes in T s have a more pronounced effect on conductivity compared to changes in d ts ; however, variations in structure do not appear to be well-correlated with conductivity for samples in the 2000–3200 S/cm range. These results suggest that incorporation and activation of Ga is of key importance when attempting to obtain GZO films with conductivities greater than 2000 S/cm.