Correlation between carrier transport and orientation evolution of polycrystalline transparent conductive Al-doped ZnO films

We have been developing a deposition technology to achieve Al-doped ZnO (AZO) polycrystalline films with a well-defined (0001) orientation. We propose the use of very thin critical layers (CLs) made from Ga-doped ZnO (GZO) films deposited by ion plating with direct-current arc discharge, which strongly affect the orientation of AZO films deposited by direct-current magnetron sputtering. The Al2O3 content in the sputtering target was 0.5 wt.%. 500-, 200- and 100-nm-thick AZO films with CLs exhibited high-Hall-mobility values of 50.1 cm2/Vs, 40.2 cm2/Vs and 32.5 cm2/Vs, respectively, compared with those of CL-free AZO films. The presence of CLs with a preferential c-axis orientation as interfaces between AZO films and glass substrates plays a critical role in producing AZO films having a textured polycrystalline structure with a well-defined (0001) orientation.