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Switching from weakly to strongly limited injection in self-aligned, nano-patterned organic transistors

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ABSTRACT

Organic thin-film transistors for high frequency applications require large transconductances in combination with minimal parasitic capacitances. Techniques aiming at eliminating parasitic capacitances are prone to produce a mismatch between electrodes, in particular gaps between the gate and the interlayer electrodes. While such mismatches are typically undesirable, we demonstrate that, in fact, device structures with a small single-sided interlayer electrode gap directly probe the detrimental contact resistance arising from the presence of an injection barrier. By employing a self-alignment nanoimprint lithography technique, asymmetric coplanar organic transistors with an intentional gap of varying size (< 0.2 μm) between gate and one interlayer electrode are fabricated. An electrode overlap exceeding 1 μm with the other interlayer has been kept. Gaps, be them source or drain-sided, do not preclude transistor operation. The operation of the device with a source-gate gap reveals a current reduction up to two orders of magnitude compared to a source-sided overlap. Drift-diffusion based simulations reveal that this marked reduction is a consequence of a weakened gate-induced field at the contact which strongly inhibits injection.

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(a) Transfer characteristics for alignment types indicated Fig. 1b,c corrected for the onset voltage Von. Shown is the drain current when operating the device with the source on side B (circles), i.e., with a gap to the gate electrode (open circles) in devices III-V, and with the source on side A (squares). Note that devices II and III as well as IV and V have comparable channel lengths. VDS = −14 V for all measured curves; (b) Difference between onset voltages, ΔVon = Von,B − Von,A, and its standard deviation for two batches of devices (diamonds and hexagons). The channel width of the devices is W = 150 μm.
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f2: (a) Transfer characteristics for alignment types indicated Fig. 1b,c corrected for the onset voltage Von. Shown is the drain current when operating the device with the source on side B (circles), i.e., with a gap to the gate electrode (open circles) in devices III-V, and with the source on side A (squares). Note that devices II and III as well as IV and V have comparable channel lengths. VDS = −14 V for all measured curves; (b) Difference between onset voltages, ΔVon = Von,B − Von,A, and its standard deviation for two batches of devices (diamonds and hexagons). The channel width of the devices is W = 150 μm.

Mentions: Figure 2a compiles the transfer characteristics IDS(VGS) obtained for the two measurement configurations in the saturation regime for all the alignment types I-V. To directly compare the drain-source currents from the two configurations, all curves have been onset voltage corrected (cf. Supplementary Figure S2 for uncorrected curves).


Switching from weakly to strongly limited injection in self-aligned, nano-patterned organic transistors
(a) Transfer characteristics for alignment types indicated Fig. 1b,c corrected for the onset voltage Von. Shown is the drain current when operating the device with the source on side B (circles), i.e., with a gap to the gate electrode (open circles) in devices III-V, and with the source on side A (squares). Note that devices II and III as well as IV and V have comparable channel lengths. VDS = −14 V for all measured curves; (b) Difference between onset voltages, ΔVon = Von,B − Von,A, and its standard deviation for two batches of devices (diamonds and hexagons). The channel width of the devices is W = 150 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037384&req=5

f2: (a) Transfer characteristics for alignment types indicated Fig. 1b,c corrected for the onset voltage Von. Shown is the drain current when operating the device with the source on side B (circles), i.e., with a gap to the gate electrode (open circles) in devices III-V, and with the source on side A (squares). Note that devices II and III as well as IV and V have comparable channel lengths. VDS = −14 V for all measured curves; (b) Difference between onset voltages, ΔVon = Von,B − Von,A, and its standard deviation for two batches of devices (diamonds and hexagons). The channel width of the devices is W = 150 μm.
Mentions: Figure 2a compiles the transfer characteristics IDS(VGS) obtained for the two measurement configurations in the saturation regime for all the alignment types I-V. To directly compare the drain-source currents from the two configurations, all curves have been onset voltage corrected (cf. Supplementary Figure S2 for uncorrected curves).

View Article: PubMed Central - PubMed

ABSTRACT

Organic thin-film transistors for high frequency applications require large transconductances in combination with minimal parasitic capacitances. Techniques aiming at eliminating parasitic capacitances are prone to produce a mismatch between electrodes, in particular gaps between the gate and the interlayer electrodes. While such mismatches are typically undesirable, we demonstrate that, in fact, device structures with a small single-sided interlayer electrode gap directly probe the detrimental contact resistance arising from the presence of an injection barrier. By employing a self-alignment nanoimprint lithography technique, asymmetric coplanar organic transistors with an intentional gap of varying size (< 0.2 μm) between gate and one interlayer electrode are fabricated. An electrode overlap exceeding 1 μm with the other interlayer has been kept. Gaps, be them source or drain-sided, do not preclude transistor operation. The operation of the device with a source-gate gap reveals a current reduction up to two orders of magnitude compared to a source-sided overlap. Drift-diffusion based simulations reveal that this marked reduction is a consequence of a weakened gate-induced field at the contact which strongly inhibits injection.

No MeSH data available.


Related in: MedlinePlus