Effect of dopant sites on the electric properties of Ga-doped ZnO

Gallium-doped ZnO (GZO) is of significant importance in various fields including optoelectronic devices, gas sensors and so on. This is primarily attributed to its remarkable advantage: its optical and electrical properties can be tuned via precisely controlling the Ga doping. In this work, a series of undoped and gallium-doped ZnO nanoparticles with various doping concentrations were synthesized by the polymer pyrolysis method and the GZO ceramics were obtained through high-temperature sintering. It is interestingly found that when the Ga doping concentration is 2 mol%, the band-gap of the sintered GZO materials reaches a minimum value of 3.08 eV, and its electrical resistivity drops down to 1.19 × 10 −3 Ω·cm. The X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectrometer (ICP-OES) measurements confirm the successful incorporation of Ga 3+ ions into ZnO lattice in two types, i.e., substitutional and interstitial Ga 3+ ions doping. The synergistic and competitive effects of the two doping types cause different trends in the lattice constant , oxygen vacancy concentration, and bandgap energy of ZnO, thereby significantly influencing the electrical properties.