Relationship between electrical and optical characterization of Ga-doped ZnO thin films deposited by magnetron sputtering

Abstract

Introduction: Transparent conducting films have received much attention in energy conversion applications. To replace high-cost indium-tin-oxide (ITO), Ga-doped ZnO (GZO) film is considered due to its high conductivity, good transparency, low cost, and low toxicity.

Methods: GZO and pure ZnO films were deposited on glass substrates by dc magnetron sputtering. The crystalline structure of the samples was verified by using X-ray diffraction. In particular, the relationship between the electrical and optical characterization of the GZO film was investigated through the plasma wavelength obtained from transmittance and reflectance spectra. Meanwhile, carrier transport was directly confirmed by Hall effect-based measurements.

Results: The GZO film shows a hexagonal wurtzite structure, with successful incorporation of Ga into the ZnO lattice. Ga doping increases the carrier concentration, leading to a decrease in the resistivity of the film. This study also discusses the correlation of carrier transport obtained from Hall effect-based measurements and optical spectroscopies. Here, we extracted the optical carrier concentration and optical mobility from the plasma wavelength and compared them with the Hall data.

Conclusion: The dependence of carrier transport on ionized impurity scattering can be pointed out. It proposes an effective way to qualitatively predict the electrical characteristics and transport properties of thin films via optical transmittance and reflectance analysis.