High-performance pentacene OTFT by incorporating Ti in LaON gate dielectric

Pentacene organic thin-film transistors (OTFT) using high-k LaTiON gate dielectric with different Ti contents are investigated. The La_xTi_(1-x)ON films (with x = 1, 0.87, 0.76, and 0.67) are deposited by reactive sputtering followed by an annealing in N₂ at 200 °C. The OTFT with La_0.87Ti_0.13ON can achieve a high carrier mobility of 2.6 cm²/V·s, a small threshold voltage of -1.5 V, a small sub-threshold swing of 0.07 V/dec, and a small hysteresis of 0.17 V. AFM and X-ray photoelectron spectroscopy reveal that Ti can suppress the hygroscopicity of La oxide to achieve a smoother dielectric surface, which can result in larger pentacene grains and thus higher carrier mobility. All the devices show a clockwise hysteresis because both the LaOH formation and Ti incorporation can generate acceptor-like traps in the gate dielectric.