• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.54.1-54.1
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• 2012

Recent significant development of organic electronics is worthy of notice for its practical application as well as fundamental understandings. Complementary-like logic circuit is a key factor to realize actual operating organic electronic devices since its advantages of low power dissipation, good noise margin and stable operations. In this reason, studies on ambipolar properties of organic materials which can act as either n-type or p-type are getting more attentions. Performances of ambipolar transistors vary a lot along its molecular structures and film properties. When properly fabricated, balanced hole and electron mobilities over 1 cm2/Vs were observed recently. Study of charge transport in ambipolar organic transistors to understand this high performance was carried out through charge modulation spectroscopy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.3
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• pp.180-184
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• 2017

In this study, we examine the electrical properties of diketopyrrolopyrrole (DPP) containing polymer semiconductors that have been reported to show high performance with ambipolar characteristics. We prepared three different DPP based polymer semiconductors (PDPPTPT, PDPP3T, and PDPP2T-TT) and fabricated organic thin film transistors (OTFTs) with ambipolar polymer semiconductors as an active layer. All three DPP polymers showed only p-type properties at initial measurements. However, after annealing in vacuum oven for 24 hours, it was found that the DPP based polymers have both p-type and n-type properties. It is speculated that the residual impurities supposedly regarded as a strong electron trap source were eliminated during the vacuum process.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.272-277
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• 2011

The ambipolar behavior of tunneling field-effect transistors (TFETs) has been investigated quantitatively by introducing a novel parameter: ambipolarity factor (${\nu}$). It has been found that the malfunction of TFET can result from the ambipolar state which is not on- or off- state. Therefore, the effect of ambipolar behavior on the device performance should be parameterized quantitatively, and this has been successfully evaluated as a function of device structure, gate oxide thickness, supply voltage, drain doping concentration and body doping concentration by using ${\nu}$.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.137-140
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• 2007

We prepared ambipolar organic field-effect transistors and observed blue emission when both hole and electron accumulation layers were in the channel. We found that the reduction of carrier traps and controlling devices' preparation and measurement conditions were crucial for ambipolar operation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.164.2-164.2
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• 2014

In order to combine advantages of ZnO thin film transistors (TFTs) with a high on-off ratio and graphene TFTs with extremely high carrier mobility, we present a facile methodology for fabricating ZnO thin film/graphene hybrid two-dimensional TFTs. Hybrid TFTs exhibited ambipolar behavior, an outstanding electron mobility of $329.7{\pm}16.9cm^2/V{\cdot}s$, and a high on-off ratio of $10^5$. The ambipolar behavior of the ZnO/graphene hybrid TFT with high electron mobility could be due to the superimposed density of states involving the donor states in the bandgap of ZnO thin films and the linear dispersion of monolayer graphene. We further established an applicable circuit model for understanding the improvement in carrier mobility of ZnO/graphene hybrid TFTs.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.9-10
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• 2006

Recent work in our laboratory has focused on the molecular and supramolecular engineering of conjugated polymers and oligomers for device applications, including light emitting diodes for displays and lighting, photovoltaic cells, and thin film transistors. A central finding is that the supramolecular structure of conjugated polymers can have a dominant influence on their properties and the performance of devices. Some major results include: highly efficient RGB light-emitting diodes from polymers and oligomers; high mobility n-channel polymer field effect transistors; ambipolar thin film transistors from copolymer semiconductors; and self-assembly and ambipolar charge transport in polymer nanowires.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.129-134
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• 2018

Herein, we report the manufacture of high-performance, ambipolar organic field-effect transistors (OFETs) and complementary-like electronic circuitry based on a blended, polymeric, semiconducting film. Relatively high and well-balanced electron and hole mobilities were achieved by incorporating a small amount of ionic additives. The equivalent P-channel and N-channel properties of the ambipolar OFETs enabled the manufacture of complementary-like inverter circuits with a near-ideal switching point, high gain, and good noise margins, via a simple blanket spin-coating process with no additional patterning of each active P-type and N-type semiconductor layer.

• Carbon letters
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• v.13 no.1
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• pp.17-22
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• 2012

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.193-194
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• 2018

Common transistor has unipolar characteristics in accordance with the doping carriers and operation by the threshold voltage, which is related to the stability. It is required the low threshold voltage of transistors to increase the stability of devices. The sensing ability is about the detection of how low current, therefore there is difference between the low current and leakage current. This study researched the ambipolar characteristics of transistors with very low currents to define the difference between common n-type transistors with unipolar properties.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1149-1154
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• 2014

To observe the tunneling phenomenon of oxide semiconductor transistor, The Indium-gallum-zinc-oxide thin film transistors deposited on SiOC as a gate insulator was prepared. The interface characteristics between a dielectric and channel were changed in according to the properties of SiOC dielectric materials. The transfer characteristics of a drain-source current ($I_{DS}$) and gate-source voltage ($V_{GS}$) showed the ambipolar or unipolar features according to the Schottky or Ohmic contacts. The ambipolar transfer characteristics was obtained at a transistor with Schottky contact in a range of ${\pm}1V$ bias voltage. However, the unipolar transfer characteristics was shown in a transistor with Ohmic contact by the electron trapping conduction. Moreover, it was improved the on/off switching in a ambipolar transistor by the tunneling phenomenon.