Characterization of a pentacene thin-film transistor with a HfO ₂/Al₂O₃ gate insulator

We fabricated pentacene thin-film transistors on HfO₂/Al ₂O₃ gate insulator layers in an ultra-high vacuum system for the first time. The HfO₂/Al₂O₃ was used as a gate insulator to decrease the operating voltage of the pentacene thin-film transistors. The field-effect mobility of the devices with HfO ₂/Al₂O₃ was obtained by using the I-V characteristics, and the value was 0.024 cm²/Vs. The threshold voltage of the pentacene thin-film transistors with HfO₂/Al ₂O₃ was decreased dramatically compared to that for devices using SiO₂ (15.3 → -0.25 V). Therefore, a thin HfO ₂/Al₂O₃ gate insulator layer can be used in pentacene thin-film transistors to lower the operating voltage.