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

Abstract

Y3+ (0, 6, 12, or 20 mol%)‐doped In2O3 (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 Y3+ (12 mol%)‐doped In2O3 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 cm2 V−1 s−1, 6.74 V, 1.55 × 105, and 2.37 V decade−1, respectively. The yttrium ion can act as the carrier suppressor to reduce the carrier concentration of In2O3 thin film because of its lower electronegativity (1.22) and standard electrode potential (−2.372 V). The carrier concentrations and conductivities of In2O3 thin films decrease from 2.5 × 1014 to 3.8 × 1011 cm−3, and 14.3 to 1.5 × 10−4 S m−1, respectively, with the increase of Y3+ doping concentrations from 0 to 12 mol%. In addition, the Y3+ (12 mol%)‐doped In2O3 thin film also possesses the minimal surface roughness (4.19 nm) and lowest trap states (1.07 × 1013). Therefore, by Y3+ doping the electrical properties of In2O3 thin films can be improved to match the basic requirement of the TFT devices.