Solution-based SnGaO thin-film transistors for Zn- and In-free oxide electronic devices

Oxide-based electronics call for low-cost and stable semiconductors to reduce cost and enable long-term operations. Transistors based on Sn show high field-effect mobility but generally exhibit weak stability and difficulty in solution-processed patterning. Here, we report solution-processed tin-gallium-oxide (SnGaO) thin-film transistors (TFTs) for In- and Zn-free electronics. Different from tin oxide, the amorphous SnGaO semiconductor features a wide bandgap of 4.6 eV, can be wet-etched and patterned by photolithography, and exhibits a large on-off ratio and good device stability in TFTs. The films are deposited via a sol-gel process and, in the photoelectron spectra, they exhibit typical signals of Sn⁴⁺ and Ga³⁺, which act as the electron provider and suppresser, respectively. By varying the elemental ratios, the average field-effect mobility could be well controlled over a wide range from 0.66 to 9.82 cm²/V s, the maximum mobility can reach 12 cm²/V s, and the on/off ratio is above 10⁶. The devices exhibited good stability for positive and negative bias stressing as well as with illumination, probably attributed to Ga-O bonds which are stronger than the weak Zn-O bonds. The presented studies may provide useful information to understand thin-film devices based on tin oxide and gallium oxide semiconductors. © 2018 Author(s).