High-gain, low-voltage unipolar logic circuits based on nanoscale flexible organic thin-film transistors with small signal delays

One of the circuit topologies for the implementation of unipolar integrated circuits (circuits that use either p -channel or n-channel transistors, but not both) is the zero-VGS architecture. Zero-VGS circuits often provide ex-cellent static performance (large small-signal gain and large noise margins), but they suffer from the large signal delay imposed by the load transistor. To address this limitation, we have used electron-beam lithography to fabricate zero-VGS circuits based on organic transistors with channel lengths as small as 120 nm on flexible poly-meric substrates. For a supply voltage of 3 V, these circuits have characteristic signal-delay time constants of 14 ns for the low-to-high transition and 560 ns for the high-to-low transition of the circuit's output voltage. These signal delays represent the best dynamic performance reported to date for organic transistor-based zero-V-GS circuits. The signal-delay time constant of 14 ns is also the smallest signal delay reported to date for flexible organic transistors.