High-mobility pentacene thin-film transistor by using La_xTa_(1-x)O_y as gate dielectric

Pentacene organic thin-film transistors (OTFTs) using La_xTa _(1-x)O_y as gate dielectric with different La contents (x = 0.227, 0.562, 0.764, 0.883) have been fabricated and compared with those using Ta oxide or La oxide. The OTFT with La _0.764Ta_0.236O_y can achieve a carrier mobility of 1.21 cm² V^-1s^-1s, which is about 40 times and two times higher than those of the devices using Ta oxide and La oxide, respectively. As supported by XPS, AFM and noise measurement, the reasons lie in that La incorporation can suppress the formation of oxygen vacancies in Ta oxide, and Ta content can alleviate the hygroscopicity of La oxide, resulting in more passivated and smoother dielectric surface and thus larger pentacene grains, which lead to higher carrier mobility.