Doping Effects of Various Carrier Suppressing Elements on Solution-Processed SnOx-Based Thin-Film Transistors

We have studied indium-free, solution-processed thin-film transistors (TFTs) based on tin-based oxide (SnO_x) semiconductors with various dopants. The dopants include aluminum (Al), zirconium (Zr), and yttrium (Y) for their electron-suppressing properties and elemental abundance. A series of doping ratio has been studied and the doped devices exhibit improved switching characteristics as compared with pure SnO_x-based TFTs. A SnO_x-based TFT having a Zr-to-Sn ratio of 6.67% shows high performance with saturation mobility of 3.1 cm²/Vs, a turn on voltage of -5.4 V, and an ON- OFF current ratio of 4.9 × 10⁶. X-ray photoelectronic spectroscopy studies were used to confirm that Zr can suppress oxygen vacancies effectively and significantly reduce carrier concentration. Furthermore, low-voltage SnZrO TFTs based on a solution-processed ZrO₂ dielectric layer were fabricated and performed at high saturation mobility of 10.9 cm²/Vs. This research may provide new valuable insights for improving SnO_x-based TFT performance.