High-performance organic thin-film transistor by using LaNbO as gate dielectric

Abstract

Pentacene organic thin-film transistors (OTFTs) using LaxNb(1-x)Oy as gate dielectric with different La contents (x=0.347, 0.648) have been fabricated and compared with those using Nb oxide or La oxide. The OTFT with La0.648Nb0.352Oy as gate dielectric can achieve a high carrier mobility of 1.14cm2V-1s-1 (about 1000 times and 2 times those of the devices using Nb oxide and La oxide, respectively), and has negligible hysteresis of -0.130V, small sub-threshold swing of 0.280V/dec, and low threshold voltage of -1.35V. AFM and XPS reveal that La can suppress the formation of oxygen vacancies in Nb oxide while Nb can alleviate the hygroscopicity of La oxide, which results in a more passivated and smoother dielectric surface, leading to larger pentacene grains grown and thus higher carrier mobility. The OTFT with Nb oxide has an anticlockwise hysteresis but the device with La oxide shows an opposite direction. This can be explained in terms of donor-like traps due to oxygen vacancies and acceptor-like traps originated from hydroxyl ions formed after La2O3 absorbing water moisture.