High figure-of-merit in Al-doped ZnO thin films grown by ALD through the Al content adjustment

The development of transparent conductive materials is of great interest for a wide variety of semiconducting devices in the fields of optoelectronics and photovoltaics. Here, we optimize the growth and properties of aluminum-doped ZnO (AZO) thin films as an eco-friendly transparent electrode by using atomic layer deposition (ALD) with diethylzinc (DEZn), water vapor and trimethylaluminium (TMA) as zinc, oxygen, and aluminum chemical precursors, respectively. The cycle ratio of DEZn to TMA using ALD is adjusted to control the Al atomic concentration over a broad range of 0.3 - 6.7% while optimizing the structural, optical, and electrical properties of AZO thin films. By incorporating a sufficient amount of Al dopants around 1.1%, we obtain a high quality AZO thin film exhibiting a low electrical resistivity of 6.3 x 10(-4) Omega center dot cm. This AZO thin film grown on quartz substrate also demonstrates an average optical transmittance in the visible range above 85% as well as a high figure-ofmerit of 6.4 x 10(-3) Omega(-1), while maintaining its highly c-axis oriented structure. The present optical and electrical properties result in the fabrication of AZO thin films by ALD with a high figure-of-merit that is highly suitable for many semiconducting devices.