Balance of Horizontal and Vertical Charge Transport in Organic Field-Effect Transistors

Sawatzki, Franz Michael; Doan, Duy Hai; Kleemann, Hans; Liero, Matthias; Glitzky, Annegret; Koprucki, Thomas; Leo, Karl

doi:10.1103/physrevapplied.10.034069

Cited by 29 publications

(44 citation statements)

References 26 publications

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“…Hence, new device concepts need to be conceived which allow for an ultra‐short channel length in conjunction with low fabrication costs. In this regard, vertical organic transistors with a channel length of ≈100 nm have generated significant interest in recent years, as the vertical dimensions of an organic transistor can be easily controlled over the nanometer regime. The organic permeable base transistor (OPBT) is a truly vertical device with a semiconductor thickness in the order of 100 nm.…”

Section: Introductionmentioning

confidence: 99%

“…In this regard, vertical organic transistors with a channel length of ≈100 nm have generated significant interest in recent years, [4][5][6][7][8][9][10] as the vertical dimensions of an organic transistor can be easily controlled over the nanometer regime. Hence, new device concepts need to be conceived which allow for an ultra-short channel length in conjunction with low fabrication costs.…”

mentioning

confidence: 99%

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Electrically Stable Organic Permeable Base Transistors for Display Applications

Dollinger

Iseke

Guo

et al. 2019

Adv Elect Materials

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Unfortunately, high-resolution patterning techniques operating in the nanometer regime are costly and currently incompatible with the promise of low-cost flexible electronics. Hence, new device concepts need to be conceived which allow for an ultra-short channel length in conjunction with low fabrication costs. In this regard, vertical organic transistors with a channel length of ≈100 nm have generated significant interest in recent years, [4][5][6][7][8][9][10] as the vertical dimensions of an organic transistor can be easily controlled over the nanometer regime. The organic permeable base transistor (OPBT) is a truly vertical device with a semiconductor thickness in the order of 100 nm. Due to the extraordinarily short channel and a reduced influence of the contact resistance, [11] the OPBT can drive very large current densities above 1 kA cm −2[12] and reaches record-high transition frequencies of 40 MHz, [3] making it the fastest organic transistor to date. The transistor consists of a vertical stack of three electrodes separated by organic semiconductor layers. The outer electrodes constitute emitter and collector, while the central electrode is the base. It has native nano-sized holes, making it permeable for electrons. Current leakage into the base is prevented by a native oxide film around the electrode. In the on-state, a charge-accumulation channel at the oxide interface is formed, ensuring efficient charge transport through the base, while in the off-state the base potential hinders the charge conduction through the pinholes. Figure 1 shows a cross-sectional transmission electron microscopy (TEM) image of an OPBT with C 60 semiconductor layers and the ultra-thin permeable base electrode of aluminum.These advances enable a broad range of possible applications for OPBTs, including display driver circuits where high currents and fast switching are needed, [13] and radio-frequency identification (RFID) systems with MHz operation. [14,15] Realworld applications, however, require a number of other properties like integrateablity, low power consumption, and stability. OPBTs operate on low voltages, generally enabling facile integration into electronic circuits. The static power consumption of OPBTs was recently dramatically reduced by the introduction of a controlled base oxidation technique. [16] Stability, though, has not yet been studied for OPBTs and there is little research regarding the behavior of short-channel vertical organic transistors under continued electrical stress.Vertical organic permeable base transistors (OPBT) can drive large current densities of kA cm −2 and achieve record-high transition frequencies of up to 40 MHz. They are therefore an interesting candidate for numerous applications, including the use in active-matrix organic light emitting display (AMOLED) backplanes. However, the transistor characteristics are required to be stable against electrical stress. Here, the threshold voltage shifts under current-and voltage-stress conditions over various temperatures and illumination condi...

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Electrically Stable Organic Permeable Base Transistors for Display Applications

Dollinger

Iseke

Guo

et al. 2019

Adv Elect Materials

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“…While Nakamura et al employed a shadow mask system for this patterning step resulting in an overlap of several micrometers, Kleemann et al developed several techniques over the years in order to bring this overlap down to the nanometer scale. Among these techniques are: lift‐off processes, complex dual‐step photolithography methods, and photolithography combined with wet‐etching . In particular, the development of a photolithographic process including wet‐etching resulted in an overlap of ≤50 nm which leads to an overall channel length of these pseudo‐VOFETs in the range of 100–200 nm.…”

Section: Overview Over Device Principles and State‐of‐the‐artmentioning

confidence: 99%

“…Additionally, they argued that the drain‐source voltage mainly drops across the contacts (including the resistance of the semiconducting film between the source electrode to the gate insulator) and hence the linear and saturation regimes are not expected to be observed for these devices. Later, Sawatzki et al developed a more detailed model for the transport in pseudo‐VOFETs by focusing on the role of the lateral overlap of the charge‐blocking‐layer over the source electrode and the influence of a different lateral and vertical charge carrier mobility . By means of a 2D drift‐diffusion model they analyzed the charge carrier distribution within the device in order to understand how the ratio of lateral and vertical transport governs the shape of the channel.…”

Section: Overview Over Device Principles and State‐of‐the‐artmentioning

confidence: 99%

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A Review of Vertical Organic Transistors

Kleemann

Krechan

Fischer

et al. 2020

Adv Funct Materials

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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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Anodization for Simplified Processing and Efficient Charge Transport in Vertical Organic Field‐Effect Transistors

Lim

Guo

Fischer

et al. 2020

Adv Funct Materials

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Vertical organic transistors are an attractive alternative to realize short channel transistors, which are required for powerful electronic devices and flexible electronic circuits operating at high frequencies. Unfortunately, the vertical device architecture comes along with an increased device fabrication complexity, limiting the potential of this technology for application. A new design of vertical organic field‐effect transistors (VOFETs) with superior electrical performance and simplified processing is reported. By using electrochemical oxidized aluminum oxide (AlOx) as a pseudo self‐aligned charge‐blocking structure in vertical organic transistors, direct leakage current between the source and drain can be effectively suppressed, enabling VOFETs with very low off‐current levels despite the short channel length. The anodization technique is easy to apply and can be surprisingly used on both n‐type and p‐type organic semiconductor thin films with significant signs of degradation. Hence, the anodization technique enables a simplified process of high‐performance p‐type and n‐type VOFETs, paving the road toward complementary circuits made of vertical transistors.

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Balance of Horizontal and Vertical Charge Transport in Organic Field-Effect Transistors

Cited by 29 publications

References 26 publications

Electrically Stable Organic Permeable Base Transistors for Display Applications

Electrically Stable Organic Permeable Base Transistors for Display Applications

A Review of Vertical Organic Transistors

Anodization for Simplified Processing and Efficient Charge Transport in Vertical Organic Field‐Effect Transistors

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