Characterization of a pentacene thin-film transistor with a HfO2/Al2O3 gate insulator

We fabricated pentacene thin-film transistors on HfO2/Al2O3 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 HfO2/Al2O3 was obtained by using the I-V characteristics, and the value was 0.024 cm(2)/Vs. The threshold voltage of the pentacene thin-film transistors with HfO2/Al2O3 was decreased dramatically compared to that for devices using SiO2 (15.3 --> - 0.25 V). Therefore, a thin HfO2/Al2O3 gate insulator layer can be used in pentacene thin-film transistors to lower the operating voltage.