Effect of Ga Doping on the Stability and Optoelectronic Properties of ZnSnO Thin Film Transistor

The electrical, stability and optoelectronic properties of GZTO TFTs with different Ga doping concentrations were investigated. Active layers were prepared by co-sputtering GaO and ZTO targets with different sputtering powers. The experimental results show that the surface of GZTO films is smooth, which is favorable for stability. The off-state current is reduced by a factor of 10, the switching ratio is increased to 1.59 × 10⁸, and the threshold voltage shift is reduced in PBS and NBS tests. In addition, the transmittance of all devices is greater than 80% in the visible range, and the optical bandgap of the TFTs is increased from 3.61 eV to 3.84 eV after Ga doping. The current enhancement of the GZTO TFTs is more pronounced under UV irradiation, with higher responsiveness and better-sustained photoconductivity. It is proved that Ga doped into ZTO as a carrier suppressor can better combine with oxygen vacancies and reduce the concentration of oxygen vacancies and oxygen defects compared with Zn and Sn atoms, thus improving stability. GaO, as a wide bandgap material, can improve the optical bandgap of GZTO TFTs so that they can better absorb the light in the UV wavelength band, and they can be used in the field of UV photodetection.