This paper reports on a new organic thin-film transistor (OTFT) based on a dual-gate configuration. This dual-gate OTFT is useful in circuit applications from the standpoint of providing control over selected device parameters for enhanced circuit reliability. Moreover, the dual-gate structure can shield parasitic effects in vertically integrated electronics, making it particularly promising for active matrix display and imaging applications. The dual-gate OTFT also lends itself as a highly functional test structure for characterization of interface integrity of the active organic and dielectric layers. In this work, the dual-gate OTFT is fabricated using regioregular poly(3-hexylthiophene) (P3HT) as the organic semiconductor layer. The bottom-gate employs silicon dioxide (SiO2) as the gate dielectric, whereas the top-gate employs a low-temperature amorphous silicon nitride (SiNx) as the passivation dielectric. The voltage on the bottom-gate has a distinct influence on the threshold voltage, subthreshold slope, on-current, and leakage current of the top-gate TFT. Similar dependence of the bottom-gate TFT characteristics on the top-gate voltage is observed. This design provides a means of characterizing the density of states of the bottom P3HT/SiO2 and top P3HT/SiNx interfaces, and conveys insight into the underlying transport mechanisms. The ability to control selected TFT parameters (e.g., threshold voltage) using the dual-gate OTFT structure is attractive for circuit integration applications in active matrix displays and imagers.
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