Schottky barrier modulation of bottom contact SnO₂ thin-film transistors via chloride-based combustion synthesis

The enhanced carrier flow at the interface between Au and SnO₂ semiconductors, which initially form Schottky contacts, is realized using chloride-based combustion synthesis. Chloride-based combustion systems can achieve chlorine (Cl) doping effects as well as conversion to crystalline SnO₂ films at clearly lower temperatures (∼250 °C) than conventional precursors. Due to the Cl doping effect, the high carrier concentration can induce thin potential barriers at the metal/semiconductor (MS) junctions, resulting in carrier injection by tunneling. As a result, compared to conventional SnO₂ thin-film transistors, the devices fabricated by combustion synthesis exhibit significantly improved electrical performance with field-effect mobility of 6.52 cm²/Vs (∼13 times), subthreshold swing of 0.74 V/dec, and on/off ratio of ∼10⁷ below 300 °C. Furthermore, because of the enhanced tunneling carriers induced by the narrowed barrier width, the Schottky barriers are significantly reduced from 0.83 to 0.29 eV (65% decrease) at 250 °C and from 0.42 to 0.17 eV (60% decrease) at 400 °C. Therefore, chloride-based combustion synthesis can contribute to developing SnO₂-based electronics and flexible devices by achieving both high-quality oxide films and improved current flow at the MS interface with low-temperature annealing.