Effect of dopants on the structural, optical and electrical properties of sol–gel derived ZnO semiconductor thin films

Undoped, Ga-, In-, Zr-, and Sn-doped ZnO transparent semiconductor thin films were deposited on alkali-free glasses by sol–gel method. 2-methoxyethanol (2-ME) and diethanolamine (DEA) were chosen as a solvent and a stabilizer, respectively. The doping concentration was maintained at 2 at.% in the impurity doping precursor solutions. The effects of different dopants on the structural, optical, and electrical properties of ZnO thin films were investigated. XRD results show that all annealed ZnO-based thin films had a hexagonal (wurtzite) structure. ZnO thin films doped with impurity elements obviously improved the surface flatness and enhanced the optical transmittance. All impurity doped ZnO thin films showed high transparency in the visible range (>91%). The Ga- and In- doped ZnO thin films exhibited higher Hall mobility and lower resistivity than did the undoped ZnO thin film.

► Ga, In, Zr, and Sn doped ZnO semiconductor films were fabricated by sol–gel method.
► ZnO films doped with impurities can reduce grain sizes and obtain smooth surfaces.
► All impurity doped ZnO films exhibited average transmittance values over 91.0%.
► Urbach energy of impurity doped films were higher than that of the undoped film.
► The Ga-doped films exhibited the highest Hall mobility and the lowest resistivity.