• Journal of Adhesion and Interface
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• v.22 no.3
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• pp.91-97
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• 2021

By introducing an organic interlayer on the Parylene C dielectric surface, the electrical device performances and the operating stabilities of organic field-effect transistors (OFETs) were improved. To achieve this goal, hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (ODTS), as the organic interlayer materials, were used to control the surface energy of the Parylene C dielectrics. For the bare case used with the pristine Parylene C dielectrics, the field-effect mobility (μ_FET) and threshold voltage (V_th) of dinaphtho[2,3-b:2',3'-f ]thieno[3,2-b]- thiophene (DNTT) FET devices were measured at 0.12 cm²V^-1s^-1 and - 5.23 V, respectively. On the other hand, the OFET devices with HMDS- and ODTS-modified cases showed the improved μ_FET values of 0.32 and 0.34 cm²V^-1s^-1, respectively. More important point is that the μ_FET and V_th of the DNTT FET device with the ODTS-modified Parylene C dielectric presented the smallest changes during a repeated measurement of 1000 times, implying that it has the most stable operating stability. The results could be meaned that the organic interlayer, especially ODTS, effectively covers the Parylene C dielectric surface with alkyl chains and reduces the charge trapping at the interface region between active layer and dielectric, thereby improving the electrical operating stability.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.130-133
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• 2002

엑시머 레이저를 이용한 저온($450^{\circ}C$ 이하) 다결정 실리콘 박막 트랜지스터 제작 시, 소오스/드레인 이온 주입에 의한 실리콘 박막의 격자 손상은 엑시머 레이저 어닐링(Excimer Laser Annealing; ELA) 방법으로 치유한다. 그러나 게이트 전극 모서리에서의 레이저광 회절 현상으로 인해 소오스/드레인 접합부에 도달하는 레이저 에너지 밀도가 감소하여 다량의 결정 결함이 치유되지 못한 채 남게 된다. 이러한 결정 결함은 박막 트랜지스터의 전계 효과 이동도를 저하시키는 요인이 된다. 새롭게 제안한 사선 입사 엑시머 레이저 어닐링(Oblique Incidence Excimer Laser Annealing; OI-ELA) 방법으로 소오스/드레인 접합부의 결정 결함을 제거하고 다결정 박막 트랜지스터의 특성을 향상시켰다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.143-143
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• 2010

다결정 실리콘 (Poly-Si)은 LPCVD를 이용하여 $750^{\circ}C$에서 증착하였다. 증착된 실리콘 박막은 실란, 수소 및 헬륨 가스를 이용하여 증착하였다. 성장된 poly-Si의 특성은 Raman spectroscopy 및 SEM을 이용하여 분석하였다. 헬륨 가스의 양을 15 sccm으로 고정하고 실란과 수소의 가스비를 60:0에서 20:40까지 가변시켰다. 활성화 에너지는 전류-전압 측정을 통해 Arrhenius plot을 이용하여 계산하였다. 박막 트랜지스터는 quartz 기판 위에 제작되었다. 게이트 절연막으로 TEOS $SiO_2$를 이용하였으며 source 및 drain 전극으로 Al을 이용하였다. 이 때 제작된 박막 트랜지스터의 전류 점멸비, 전계 효과 이동도, SS 및 문턱 전압은 각각 $10^5$, $76\;cm^2/V-s$, 167 mV/decade 및 1.43 V이었다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.87-96
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• 1999

For analog optical transmission of narrow-band microwave signal, a novel all-optical linearization technique of electro-absorption (EA) optical modulator by using dual modulation scheme is proposed and theoretically investigated. By using the dual modulation scheme where the sub-modulator has a different length, DC bias and band-gap wavelength, the DC bias operation point where the third-order intermodulation products of ~30dB and the following increase of spurious free dynamic range (SFDR) of ~20dB wave achieved in sub-octave narrow band operation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.2
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• pp.1-6
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• 2009

The experimental results of exposing IGBT (Insulated Gate Bipolar Transistor) samples to gamma radiation source show shifting of threshold voltages in the MOSFET and degradation of carrier mobility and current gains. At low total dose rate, the shift of threshold voltage is the major contribution of current increases, but for more than some total dose, the current is increased because of the current gain degradation occurred in the vertical PNP at the output of the IGBTs. In the paper, the collector current characteristics as a function of gate emitter voltage (VGE) curves are tested and analyzed with the model considering the radiation damage on the devices for gate bias and different dose. In addition, the model parameters between simulations and experiments are found and studied.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.189.2-189.2
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• 2013

1차원 산화아연 나노구조물은 광대역 에너지 밴드갭(~3.3 eV)과 독특한 물리적 특성을 갖고 있어, 전계효과 트랜지스터(field effect transistor), 발광다이오드(light emitting diode), 자외선 광검출기 (ultraviolet photodetector) 및 태양전지(photovoltaic cell)에 널리 이용되고 있다. 특히, 1차원 산화아연 나노구조물은 직접천이형 에너지 밴드갭(direct bandgap)을 갖고 있으며, 빛으로부터 여기된 전자가 1차원 나노구조물을 통해 향상된 이동경로를 제공할 수 있어서 차세대 자외선 광검출기 응용에 대한 연구가 활발히 진행되고 있다. 한편, 수열합성법(hydrothermal method)을 통해서 1차원 산화아연 나노구조물을 비교적 간단하고 저온공정을 통해서 합성할 수 있는데, 이를 광검출기 소자구조에 응용에서 양전극에 연결하기 위해서는 복잡하고 정교한 공정이 필요하다. 이에 본 연구에서는 수열합성법을 통해 합성된 산화아연 나노로드가 포함된 에탄올 용액을 금(Au) 패턴에 drop-casting을 통해서 간단한 방법으로 metal-semiconductor-metal (MSM) 광검출기를 제작하여 광반응 특성을 분석하였다. 또한 염료를 통해 가시광을 흡수하여 광전류(photocurrent)를 발생시킬 수 있도록 염료를 흡착한 산화아연 나노로드를 이용하여 같은 구조의 MSM 광검출기를 제작하여 가시광에 대한 광반응 특성을 관찰하였다.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.65-66
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• 2006

AIGaN/GaN 고전자 이동도 트랜지스터 (High Electron Mobility Transistors, HEMTs)는 와이드 밴드-갭과 높은 항복 전계 및 우수한 채널 특성으로 인해 마이크로파 응용분야와 전력용 반도체에서 각광받고 있다. 최근, 전력 응용분야에서 요구되는 높은 항복 전압과 출력, 우수한 주파수 특성을 획득하기 인해 이중 게이트 AIGaN/GaN HEHTs에 관한 연구가 발표되고 있다. 본 논문에서는 AIGaN/GaN HEMTs에 이중 게이트를 적용하여, 두 개의 게이트와 드레인, 소스의 누설 전류를 각각 측정하여 이중 게이트 AIGaN/GaN HEMTS의 누설 전류 메커니즘을 분석하였다. 또한 제안된 소자의 $SiO_2$ 패시베이션 전 후의 누설 전류 특성을 비교하였다. $SiO_2 $ 패시베이션되지 않은 소자의 누설 전류는 드레인, 소스와 추가 게이트로부터 주 게이트로 흐른 반면, 패시베이션 된 소자 누설 전류는 드레인으로부터 주 게이트 방향의 누설 전류만 존재하였다. $SiO_2$ 패시베이션 된 소자의 누설 전류는 (87.31 nA ) 패시베이션 되지 않은 소자의 누설 전류 ( $8.54{\mu}A$ )에 비해 의게 감소하였다.

• 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.

• Journal of the Korean Vacuum Society
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• v.22 no.5
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• pp.270-275
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• 2013

Single-layer graphene layers have been synthesized by using chemical vapor deposition, subsequently transferred on 300 nm $SiO_2/Si$ and quartz substrates, and doped with $AuCl_3$ by spin coating for various doping concentrations ($n_D$) from 1 to 10 mM. Based on the $n_D$-dependent variations of Raman frequencies/peak-intensity ratios, sheet resistance, work function, and Dirac point, measured by structural, optical, and electrical analysis techniques, the p-type nature of graphene is shown to be strengthened with increasing $n_D$. Especially, as estimated from the drain current-gate voltage curves of graphene field effect transistors, the hole mobility is very little varied with increasing $n_D$, in strong contrast with the $n_D$-dependent large variation of electron mobility. These results suggest that $AuCl_3$ is one of the best p-type dopants for graphene and is promising for device applications of the doped graphene.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.219-226
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• 2013

Organic semiconductor-based soft electronics has potential advantages for next-generation electronics and displays, which request mobile convenience, flexibility, light-weight, large area, etc. Organic field-effect transistors (OFET) are core elements for soft electronic applications, such as e-paper, e-book, smart card, RFID tag, photovoltaics, portable computer, sensor, memory, etc. An optimal multi-layered structure of organic semiconductor, insulator, and electrodes is required to achieve high-performance OFET. Since most organic semiconductors are self-assembled structures with weak van der Waals forces during film formation, their crystalline structures and orientation are significantly affected by environmental conditions, specifically, substrate properties of surface energy and roughness, changing the corresponding OFET. Organo-compatible insulators and surface treatments can induce the crystal structure and orientation of solution- or vacuum-processable organic semiconductors preferential to the charge-carrier transport in OFET.