Ga-concentration-dependent optical and electrical properties of Ga-doped ZnO thin films prepared by low-temperature atomic layer deposition

With the vigorous development of information display system and solar energy conversion technology, it is crucial to develop newly indium-free, transparent conductive material (TCO). In this work, Ga-doped ZnO (GZO) thin films with excellent TCO properties were prepared by atomic layer deposition (ALD) at low-temperature. The influence of doping concentration on film performance was studied in detail by X-ray diffractometer, scanning electron microscopy, Hall-effect measurement, X-ray photoelectron spectroscopy and UV–visible spectroscopy. It has been found that the surface morphology of all as-prepared thin films is in irregular grain-like texture, and the preferred orientation and electrical properties of the GZO thin films are highly dependent on Ga-concentration. When the Ga-doping concentration is 1.16 at.% (at ZnO/Ga2O3 cycle ratio of 24:1), the GZO film exhibits the highest carrier concentration of 1.07 × 1021 cm−3, the lowest resistivity of 6.91 × 10−4 Ω cm and the highest quality factor ΦTc of 3.5 × 10−3 Ω−1. The average transmittance of the GZO thin films is better than ~ 88%. This study provides an important reference of GZO for TCO film in flexible electronic devices including display devices and other optoelectronic applications.