Improvement of electrical characteristics in the solution-processed nanocrystalline indium oxide thin-film transistors depending on yttrium doping concentration

摘要

Y~(3+) (0,6,12, or 20 mol%)-doped In_2O_3 (YInO; YIO) thin films were fabricated by the sol-gel spin-coating technique, and they were used as the active layer of thin-film transistor (TFT) devices. The YIO-TFTs operate in the n-channel enhancement mode and exhibit a well-defined pinch-off and saturation region. The Y~(3+) (12mol%)-doped In_2O_3 TFT possesses the optimal performance, and its field-effect mobility in the saturated regime, threshold voltage, on-off ratio, and S factor are 0.95 cm~2 V~(-1)s~(-1),6.74 V, 1.55 × 10~5, and 2.37 V decade~(-1), respectively. The yttrium ion can act as the carrier suppressor to reduce the carrier concentration of In_2O_3 thin film because of its lower electronegativity (1.22) and standard electrode potential (-2.372 V). The carrier concentrations and conductivities of In_2O_3 thin films decrease from 2.5 × 10~(14) to 3.8 × 10~(11) cm~(-3), and 14.3 to 1.5 × 10~(-4) S m~(-1), respectively, with the increase of Y~(3+) doping concentrations from 0 to 12 mol%. In addition, the Y~(3+) (12 mol%)-doped In_2O_3 thin film also possesses the minimal surface roughness (4.19 nm) and lowest trap states (1.07 × 10~(13)). Therefore, by Y~(3+) doping the electrical properties of In_2O_3 thin films can be improved to match the basic requirement of the TFT devices.