Split‐Gate Organic Field‐Effect Transistors for High‐Speed Operation

Uemura, Tomomasa; Matsumoto, Takuji; Miyake, K.; Uno, Mayumi; Ohnishi, Shigeo; Kato, Tatsuya; Kobayashi, Masayuki; Shoji, Shuichi; Hamada, Mototsugu; Kang, Myeong Jin; Takimiya, Kazuo; Mitsui, Chikahiko; Okamoto, Toshihiro; Takeya, Jun

doi:10.1002/adma.201304976

Cited by 33 publications

(30 citation statements)

References 23 publications

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“…However, while promising results in AC operation of organic FETs have been reported, with a maximum operating frequency as high as 27.7 MHz29, record values have been so far mainly achieved by adopting photolithographic steps30313233 and/or single crystal semiconductors34. To date, one order-of-magnitude lower operating frequencies have been demonstrated when mask-less, scalable techniques were used, with a maximum of 3.3 MHz25353637.…”

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confidence: 99%

Direct-written polymer field-effect transistors operating at 20 MHz

Perinot

Kshirsagar

Malvindi

et al. 2016

Sci Rep

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Printed polymer electronics has held for long the promise of revolutionizing technology by delivering distributed, flexible, lightweight and cost-effective applications for wearables, healthcare, diagnostic, automation and portable devices. While impressive progresses have been registered in terms of organic semiconductors mobility, field-effect transistors (FETs), the basic building block of any circuit, are still showing limited speed of operation, thus limiting their real applicability. So far, attempts with organic FETs to achieve the tens of MHz regime, a threshold for many applications comprising the driving of high resolution displays, have relied on the adoption of sophisticated lithographic techniques and/or complex architectures, undermining the whole concept. In this work we demonstrate polymer FETs which can operate up to 20 MHz and are fabricated by means only of scalable printing techniques and direct-writing methods with a completely mask-less procedure. This is achieved by combining a fs-laser process for the sintering of high resolution metal electrodes, thus easily achieving micron-scale channels with reduced parasitism down to 0.19 pF mm−1, and a large area coating technique of a high mobility polymer semiconductor, according to a simple and scalable process flow.

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confidence: 99%

Direct-written polymer field-effect transistors operating at 20 MHz

Perinot

Kshirsagar

Malvindi

et al. 2016

Sci Rep

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“…[2][3][4][5][6][7][8][9][10][11][12] Therefore by scaling the channel length down to 10-1 μm, in principle OTFTs should be able to operate at relatively high (1-10 MHz) frequencies at reasonable (<10 V) applied voltages. [ 13 ] In practice, apart from some reports, [13][14][15][16][17][18][19][20][21][22] this is often not easy to achieve because of injection issues: [ 23,24 ] contact resistances tend to become dominant over the channel resistance in short channel transistors reducing the expected improvement of device performances. [ 25 ] This situation is severely limiting the range of applications for OTFTs.…”

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confidence: 99%

Injection Length in Staggered Organic Thin Film Transistors: Assessment and Implications for Device Downscaling

Natali

Chen

Maddalena

et al. 2016

Adv Elect Materials

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of organic semiconductors show carrier mobility in excess of 5 cm 2 V −1 s −1 when employed as active materials in long (>10 μm) channel organic thin fi lm transistors (OTFT). [2][3][4][5][6][7][8][9][10][11][12] Therefore by scaling the channel length down to 10-1 μm, in principle OTFTs should be able to operate at relatively high (1-10 MHz) frequencies at reasonable (<10 V) applied voltages. [ 13 ] In practice, apart from some reports, [13][14][15][16][17][18][19][20][21][22] this is often not easy to achieve because of injection issues: [ 23,24 ] contact resistances tend to become dominant over the channel resistance in short channel transistors reducing the expected improvement of device performances. [ 25 ] This situation is severely limiting the range of applications for OTFTs. [ 26 ] Indeed contact resistances arise from contact/semiconductor interface properties hence they are not expected to scale with the transistor channel length. To address this issue not only suitable modifi cations of the contact/semiconductor interface aimed at enhancing the contact injecting properties have to be implemented, [ 27 ] but also the device topology has to be considered. Staggered OTFTs, where the contacts and the transistor channel do not lie in the same plane, are usually characterized by lower contact resistances than coplanar ones: [ 28 ] while in these latter the injection area is limited by the accumulated channel depth (few nanometers), in the former the overlap between gate and source/drain contacts (many micrometers or even tens of micrometers) can be exploited, as shown in Figure 1 . The gate/contact overlapping length has to be suitably engineered: on the one hand it should be large enough to accommodate the injected current and to minimize contact resistances; but on the other hand it should not be too large because overlapping areas not effectively involved in injection solely result in additional parasitic capacitances that deteriorate the device speed. [ 13,29 ] It is therefore important to quantify the injection length, which is the length over which sizeable carrier injection occurs. [ 30,31 ] Despite the large number of studies on contact effects in OTFTs, [ 24,32 ] few of them discuss the effect of the gate to contact overlap: Xu et al. found a relationship between the optimal contact length and the semiconductor thickness in staggered OTFT. [ 33 ] Park et al. found that threshold voltage, fi eld effect mobility and contact resistances are affected by the contact length in staggered OTFT; [ 34 ] Wang et al. simulated the effect of contact length scaling. [ 35 ] Ante et al. studied the effect of contact In staggered thin fi lm transistors, the injection length is the fraction of the gate to contact overlap that is effectively involved in current injection. Its assessment is important to properly downscale device dimensions. In fact, in order to increase transistor operation speed, the whole device footprint should be downscaled, which means both the gate to contact overlap and the channel length, as ...

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“…Compilation of a) transition frequency values and b) transition frequencies normalized by driving voltage V DS versus time in organic transistors, using various technologies …”

Section: Introduction: Vertical Versus Lateral Organic Transistorsmentioning

confidence: 99%

A Review of Vertical Organic Transistors

Kleemann

Krechan

Fischer

et al. 2020

Adv Funct Materials

120

110

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Powerful electronic devices require performant short‐channel transistors. For organic electronics, though, promising low‐cost and flexible electronic circuits, high processing costs for short channel devices are not acceptable. In this regard, vertical organic transistors (VOTs) are an attractive alternative, and in fact, today they reach the highest transition frequency (40 MHz) and the highest footprint current density (>1 MA cm−2) among all organic transistors. Here, all VOT concepts are reviewed, while discussing device physics, integration approaches, and highlighting the recent developments. The upcoming challenges for the VOT technology are also presented with a guideline for further developments.

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Split‐Gate Organic Field‐Effect Transistors for High‐Speed Operation

Cited by 33 publications

References 23 publications

Direct-written polymer field-effect transistors operating at 20 MHz

Direct-written polymer field-effect transistors operating at 20 MHz

Injection Length in Staggered Organic Thin Film Transistors: Assessment and Implications for Device Downscaling

A Review of Vertical Organic Transistors

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