• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.289-292
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• 2012

Au electrodes modified with self-assembled monolayers (SAMs) were used to control the work function of source/drain electrodes in triethylsilylethynyl anthradithiophene (TES ADT)-based organic thin film transistors (OTFTs). By using benzothiol (BT) and pentafluorobenzothiol (PFBT) SAMs, the hole injection barrier between Au and the highest occupied molecular orbital (HOMO) of TES ADT was controlled. After a solvent annealing, TES ADT OTFTs with PFBT SAM-treated Au electrodes were found to exhibit high field-effect mobilities of $0.05\;cm^2/Vs$ and on/off current ratios of $10^6$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.381-382
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• 2018

Subthreshold swings (SSs) and on-currents of four types of junctionless nanowire tunnel field-effect transistor(JLNW-TFET) are observed. Ge-Si structure for the source-channel junction has the highest drive current among Si-Si, Si-Ge, and Ge-Ge junction, and the drive current increases up to 1000 times compared to others. Minimum SS of Si-Si junction is reduced by up to 5 times more than others.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.63-69
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• 2011

In this study, we report on the novel lithographic patterning method to fabricate organic thin film field effect transistors (OTFTs) based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30 nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce $Al_2O_3$ film grown via atomic layer deposition method onto pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated micron sized pentacene FETs and measured their electrical characteristics.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.420-424
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• 1999

In this paper, an optical switching circuit and several types of all-optical transmitter/receiver circuits which are configured with photodiodes, multiple quantum-well(MQW) optical modulators, and field-effect transistors(FETs) were simulated using PSPICE and their results of these are examined and discussed. 20 $\mu\textrm{m}$ ${\times}$ 20 $\mu\textrm{m}$ of window size was used for the optical modulators and 100 $\mu\textrm{m}$ wide FETs with the transconductance value of 55 mS/mm were used for the simulations. Simulation results clearly show that in order for the high speed operation of the all-optical circuits, the size of each device should be minimized to reduce the parasitic capacitance, the circuits should be designed to operate at the wavelength where the resposivity of photodiodes becomes the maximum peak, and the use of short, high-intensity input optical signal beams is very advantageous.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.242.1-242.1
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• 2011

산화물 반도체는 높은 이동도와 낮은 공정 온도, 넓은 밴드갭으로 인한 투명성등 많은 장정을 가지고 있어 최근 많이 연구되고 있다. 그 중에서도 InGaZnO (IGZO)는 In, Ga 함유량으로 박막의 전기적 특성을 쉽게 조절할 수 있고 상온에서 비정질 상태로 증착되어 균일성에 장점이 있다. IGZO 박막을 TFT에 적용 시 MOSFET과는 다르게 축적 상태에서 채널이 형성되기 때문에 산화물 반도체 내에 캐리어 농도는 TFT 특성에 많은 영향을 미친다. 또한, 실리콘 기반의 트랜지스터는 이온 주입 및 확산 공정을 통해서 선택적으로 $10^{20}/cm^3$ 이상의 고농도 도핑을 실시하여 좋은 트랜지스터 특성을 확보할 수 있으나 IGZO 박막에는 이러한 접근이 불가능하다. 따라서 IGZO 박막의 캐리어 농도를 조절할 수 있으면 소스/드레인과 반도체의 접촉 저항 감소 및 전계 효과 이동도등 많은 특성을 개선할 수 있다. 본 연구에서는 UV light를 이용하여 IGZO 박막의 캐리어 농도를 조절하였다. IGZO 박막은 UV light 조사로 인해 Mo와 IGZO박막의 접촉저항이 $3{\times}10^3\;{\Omega}^*cm$에서 $1{\times}10^2\;{\Omega}^*cm$로 감소하였다. 이는 UV 조사로 표면에 금속-OH 결합이 생성되어 IGZO 박막의 캐리어 농도가 ${\sim}5{\times}10^{15}/cm^3$에서 ${\sim}3{\times}10^{17}/cm^3$까지 증가하기 때문이다. 또한 표면에 생성된 OH기는 강한 친수성 성질을 보여주고 표면의 높은 에너지 상태는 Self-Assembly Monolayer (SAM) 공정 적용이 가능 하다. 본 실험에서는 SAM 공정을 적용하여 IGZO-based TFT 제작에 성공하였고, 이 TFT는 UV 조사 시간에 따라 전계 효과 이동도가 0.03 $cm^2/Vs$에서 2.1 $cm^2/Vs$으로 100배 정도 증가하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.190-195
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• 2015

The detection of single nucleotide polymorphisms (SNPs) caused of mutant or genetic diseases is important to diagnosis and medicine. There are many methods have been proposed to detect SNPs. However the detection of SNPs is difficulty, because the difference of energy between complementary DNA (cDMA) and SNPs is very small. In this work, we detect the SNPs using field-effect transistors (FETs) which based on the detection of negative charge of DNA. We bias -0.3 V on the drain-source electrode at the target DNA hybridization process. The efficiency of hybridization and the amplitude of signal decrease by repulsive force between negative charge of DNA and negative bias on the electrode. However, the sensitivity of SNPs increases about 5 times from 1.7 mV to 8.7 mV.

• Journal of IKEEE
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• v.21 no.3
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• pp.284-287
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• 2017

In this study, we examined the simulated electrical characteristics of single-gated feedback field effect transistors (FBFETs) and the influence of channel length variation of the memory window characteristics through the 3D device simulation. The simulations were carried out for various channel lengths from 50 nm to 100 nm. The FBFETs exhibited zero SS(< 1 mV/dec) and a current $I_{on}/I_{off}$ ratio${\sim}1.27{\times}10^{10}$. In addition, the memory windows were 0.31 V for 50 nm-channel-length devices while no memory windows were observed for 100 nm-channel-length devices.

• Journal of Adhesion and Interface
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• v.23 no.3
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• pp.75-79
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• 2022

Graphene is a two-dimensional carbon allotrope composed of honeycomb sp² hybrid orbital bonds. It shows excellent electrical and mechanical properties and has been spotlighted as a core material for next-generation electronic devices. However, it exhibits low environmental stability due to the easy penetration or adsorption of external impurities from the formation of an unstable interface between the materials in the electronic devices. Therefore, this work aims to improve and investigate the low environmental stability of graphene-based field-effect transistors through direct growth using solid hydrocarbons as a precursor of graphene. Graphene synthesized from direct growth shows high electrical stability through reduction of change in charge mobility and Dirac voltage. Through this, a new approach to utilize graphene as a core material for next-generation electronic devices is presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.337-337
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• 2010

갈륨-질화물 (GaN) 기반의 고 전자 이동도 트랜지스터 (High Electron Mobility Transistor, HEMT)는 GaN의 큰 밴드갭 (3.4~6.2 eV), 높은 항복전계 (Ec~3 MV/cm) 및 높은 전자 포화 속도 (saturation velocity $-107\;cm{\cdot}s-1$) 특성과 AlGaN/GaN 등과 같은 이종접합구조(Heterostructure )로부터 발생하는 높은 면밀도(Sheet Concentration)를 갖는 이차원 전자가스(Two-Dimensional Electron Gas, 2DEG) 채널로 인해 차세대 고출력/고전압 소자로서 각광받고 있다. 하지만 드레인 쪽의 게이트 에지부분에 집중되는 전계로 인한 애벌린치 할복현상(Breakdown)이 발생하는 문제점이 있다. 따라서 AlGaN/GaN HEMT의 항복전압 향상을 위한 방법으로 필드플레이트(Field-Plate) 구조가 많이 사용되고 있다. 본 논문에서는 2D 시뮬레이션을 통한 AlGaN/GaN HEMT의 필드플레이트 구조 최적화를 수행하였다. 이를 위해 ATLASTM 전산모사 프로그램을 이용하여 필드플레이트 길이, 절연체 증류 및 두께에 따른 전류 전압 특성 및 전계 분산효과에 대한 전산모사를 수행하여 그 결과를 비교, 분석 하였다, 이를 바탕으로 기존의 구조에 비해 약 300%이상 향상된 항복전압을 갖는 AlGaN/GaN HEMT의 최적화된 필드 플레이트 구조를 제안하였다.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.144-152
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• 2021

Understanding charge transfer across the interface between organic semiconductor and gate insulator gives insight into the development of high-performance organic memory as well as highly stable organic field-effect transistors (OFETs). In this work, we firstly unveil a novel interfacial charge transfer mechanism, in which hole transfer from organic semiconductor to polymer insulator was nonlinearly boosted by localized states coupling. For this, OFETs based on rubrene single crystal semiconductor and Mylar gate insulator were fabricated via vacuum lamination, which allows stable repetition of lamination and delamination between semiconductor and gate insulator. The surfaces of rubrene single crystal and Mylar film were selectively degraded by photo-induced oxygen diffusion and UV-ozone treatment, respectively. Consequently, we found that the interfacial charge transfer and resultant bias-stress effect were nonlinearly boosted by coupling between localized states in rubrene and Mylar. In particular, the small number of localized states in rubrene single crystal provided fluent pathway for interfacial charge transport.