Excellent Current Drivability and Environmental Stability in Room-Temperature-Fabricated Pentacene-Based Organic Field-Effect Transistors With ${\rm HfO}_{2}$ Gate Insulators

Low-voltage-operating pentacene-based organic field-effect transistors (OFETs) with HfO₂ gate insulators have been fabricated at room temperature. Despite its thin capacitance equivalent thickness of 3.6 nm, the room-temperature-processed HfO2 gate insulator shows a low leakage current density of 1.2×10^-7 A/cm² at a gate voltage of -2 V. Pentacene films grown on the HfO2 gate insulators have a large grain size and a highly ordered molecular structure due to the appropriate surface properties of the HfO₂ gate insulators. The as-fabricated pentacene-based OFET (W/L=1300 μm/100 μm) with a HfO₂ gate insulator has a low subthreshold swing of 0.13 V/decade, a large ON/OFF current ratio of 9.8×10⁴, and a high hole mobility of 0.34 cm²V^-1s^-1 at an operating voltage of -2 V. Furthermore, the environmental stability in the room-temperature-fabricated pentacene-based OFETs with HfO2 gate insulators was investigated.