Abstract
Abstract Vertical organic field-effect transistors (VOFETs) provide an advantage over lateral ones with respect to the possibility to conveniently reduce the channel length. This is beneficial for increasing both the cut-off frequency and current density in organic field-effect transistor devices. We prepared P3HT (poly[3-hexylthiophene-2,5-diyl]) VOFETs with a surrounding gate electrode and gate dielectric around the vertical P3HT pillar junction. Measured output and transfer characteristics do not show a distinct gate effect, in contrast to device simulations. By introducing in the simulations an edge layer with a strongly reduced charge mobility, the gate effect is significantly reduced. We therefore propose that a damaged layer at the P3HT/dielectric interface could be the reason for the strong suppression of the gate effect. We also simulated how the gate effect depends on the device parameters. A smaller pillar diameter and a larger gate electrode-dielectric overlap both lead to better gate control. Our findings thus provide important design parameters for future VOFETs.
Highlights
Organic field-effect transistors (OFETs) are extensively applied in low-cost [1], flexible [2], and biocompatible [3] electronic devices
When the gate electrode does not completely cover the gate dielectric between source and drain, would it matter if the gate is close to the source or the drain? Device simulation results show that the gate effect is influenced by the position of the gate electrode when the gate electrode does not completely cover the dielectric
We have fabricated vertical organic field-effect transistors (VOFETs) that consist of pillars of poly[3-hexylthiophene-2,5-diyl] (P3HT) with a gate that completely or half surrounds the pillars
Summary
Organic field-effect transistors (OFETs) are extensively applied in low-cost [1], flexible [2], and biocompatible [3] electronic devices. It is critical to achieve high cutoff frequencies (~10 MHz) and large current densities (10e20 mA/cm2) to improve the device performance for many OFET applications, such as organic lightemitting transistors or display pixel drivers [4e6]. In addition to applying high-mobility organic semiconductors, this can be achieved by decreasing the OFET channel length [7e9]. Peer review under responsibility of Vietnam National University, Hanoi. OFETs are beneficial for low-power electronic applications, since sizeable current densities can be obtained, even operating at low voltages [10,11]. B. Xu et al / Journal of Science: Advanced Materials and Devices 2 (2017) 501e514
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