Pentacene-Based Low Voltage Organic Field-Effect Transistors with Anodized Ta_2O_5 Gate Dielectric

摘要

Pentacene-based low voltage organic field-effect transistors were realized using anodized Ta_2O_5 gate dielectrics. A Ta_2O_5 gate dielectric of thickness ～1,700 Å was obtained by anodizing a sputtered and annealed Ta film on an n-Si wafer substrate. The device exhibited values of saturation mobility, threshold voltage, and Ion/Ioff ratio (at V_ds = -5 V and V_g = 0 to -2.5 V) of 0.52 cm~2/V.s, -1.28 V, and 1.64 × 10~2, respectively. The relatively high gate leakage current was reduced by more than 40 % with a Hexamethyldisilazane (HMDS) treatment on the Ta_2O_5 gate dielectric. The HMDS treatment also resulted in slightly enhanced saturation mobility, decreased threshold voltage by a factor of two, and increased I_on/I_off ratio by more than an order of magnitude, which suggests that the characteristics of anodized Ta_2O_5 devices can be improved by a suitable surface treatment.