Physical properties of Al-doped ZnO and Ga-doped ZnO thin films prepared by direct current sputtering at room temperature

Al-doped zinc oxide (AZO) and Ga-doped zinc oxide (GZO) thin films with the same doping concentration (3.6 at%) were deposited on glass substrates at room temperature by direct current (DC) magnetron sputtering. Consequently, we comparatively studied the doped thin films on the basis of their structural, morphological, electrical, and optical properties for optoelectronic applications. Both thin films exhibited excellent optical properties with more than 85% transmission in the visible range. The GZO thin film had better crystallinity and smoother surface morphology than the AZO thin film. The conductivity of the GZO thin film was improved compared to that of the AZO thin film: the resistivity decreased from 1.01 × 10-3 to 3.5 × 10-4 Ω cm, which was mostly due to the increase of the carrier concentration from 6.5 ×1020 to 1.46 × 1021 cm-3. These results revealed that the GZO thin film had higher quality than the AZO thin film with the same doping concentration for optoelectronic applications.