• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.9
• /
• pp.1615-1622
• /
• 2008

We have fabricated the poly-silicon thin film transistor(TFT) which has the LDD-region with graded spacer. The devices of n-channel poly-si TFT's hydrogenated by $H_2$ and $H_2$/plasma processes were fabricated for the devices reliability. We have biased the devices under the gate voltage stress conditions of maximum leakage current. The parametric characteristics caused by gate voltage stress conditions in hydrogenated devices are investigated by measuring/analyzing the drain current, leakage current, threshold voltage($V_{th}$), sub-threshold slope(S) and transconductance($G_m$) values. As a analyzed results of characteristics parameters, the degradation characteristics in hydrogenated n-channel polysilicon TFT's are mainly caused by the enhancement of dangling bonds at the poly-Si/$SiO_2$ interface and the poly-Si grain boundary due to dissolution of Si-H bonds. The structure of novel proposed poly-Si TFT's are the simplicities of the fabrication process steps and the decrease of leakage current by reduced lateral electric field near the drain region.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.434-434
• /
• 2011

Electrochemical method have been employed in this work to modify the chemical vapour deposited nitrogen doped hydrogen amorphous diamond-like carbon (N-DLC) film to fabricate nickel and copper nano particle modified N-DLC electrodes. The electrochemical behaviour of the metal nano particle modified N-DLC electrodes have been characterized at the presence of glucose in electrolyte. Meanwhile, the N-DLC film structure and the morphology of metal nano particles on the N-DLC surface have been investigated using micro-Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. The nickel nano particle modified N-DLC electrode exhibits a high catalytic activity and low background current, while the advantage of copper modified N-DLC electrode is drawn back by copper oxidizations at anodic potentials. The results show that metal nano particle modification of N-DLC surface could be a promising method for controlling the electrochemical properties of N-DLC electrodes.

• Transactions of the Korean hydrogen and new energy society
• /
• v.3 no.2
• /
• pp.35-43
• /
• 1992

Thin Film yttrium, 500 nm thick, was prepared by electron beam evaportion on sapphire substrate. Film was hydrogenated at room temperature upto 1 bar hydorgen pressure without any activation process. Electrical resistivity was measured by four-point DC method in the temperature range between room temperature and 30 K for various hydorgen concentration x = 0 to 2.924 of $YH_x$ sample. Temperature dependent resistance of $YH_{2\;924}$ shows low temperature minmum at 105K ($36{\mu}{\Omega}cm$ deep), the metal-semiconductor transition at 260K, and a hysteresis, which are similar behavior to bulk $YH_x$(x>2) experimental results.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1277-1279
• /
• 1993

As a highly information-oriented society developes, various kinds of amorphous semiconductor devices, such as solar cells, electrographic printers, image sensors, and flat-panel televisions, have been developed as man/machine interfaces. This paper proposed the laser CVD techniques to deposit hydrogenated amorphous silicon thin film on glass or dielectric substrate at low temperatures. Varying the deposition conditions, we examined optical and electrical charateristics of a-Si:H film deposited by Laser CVD.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.10
• /
• pp.1694-1696
• /
• 2016

Present thin film solar cells with hydrogenated amorphous silicon oxide (a-SiO:H) as an absorber suffer from low fill factor(FF) of 61~64 [%] in spite of its benefits related to high open circuit voltage ($V_{oc}$). Since degraded quality of a-SiO:H absorber by alloying with oxygen can affect the FF, we aimed to achieve high photosensitivity by minimizing $CO_2$ gas addition. Improving optical gap($E_{opt}$) has been attained by strong hydrogen dilution combined with lowering substrate temperature down to 100 [$^{\circ}C$]. Small amount of the $CO_2$ was added in order to disturb microcrystalline formation by high hydrogen dilution. The developed a-SiO:H has high photosensitivity (${\sim}2{\times}10^5$) and high $E_{opt}$ of 1.85 [eV], which contributed to attain remarkable FF of 74 [%] and high $V_{oc}$ (>1 [V]). As a result, high power conversion efficiency of 7.18 [%] was demonstrated by using very thin absorber layer of only 100 [nm], even though we processed all experiment at extremely low temperature of 100 [$^{\circ}C$].

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.12
• /
• pp.565-569
• /
• 2006

Plasma enhanced chemical vapor deposition(PECVD) is a well established technique for the deposition of hydrogenated film of silicon nitride (SiNx:H), which is commonly used as an antireflection coating as well as passivating layer in crystalline silicon solar cell. PECVD-SiNx:H films were investigated by varying the deposition and annealing conditions to optimize for the application in silicon solar cells. By varying the gas ratio (ammonia to silane), the silicon nitride films of refractive indices 1.85 - 2.45 were obtained. The film deposited at $450^{\circ}C$ showed the best carrier lifetime through the film deposition rate was not encouraging. The film deposited with the gas ratio of 0.57 showed the best carrier lifetime after annealing at a temperature of $800^{\circ}C$. The single crystalline silicon solar cells fabricated in conventional industrial production line applying the optimized film deposition and annealing conditions on large area substrate of size $125mm{\times}125mm$ (pseudo square) was found to have the conversion efficiencies as high as 17.05 %. Low cost and high efficiency silicon solar cells fabrication sequence has also been explained in this paper.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.242-242
• /
• 2012

Transparent oxide semiconductors are increasingly becoming one of good candidates for high efficient channel materials of thin film transistors (TFTs) in large-area display industries. Compare to the conventional hydrogenated amorphous silicon channel layers, solution processed ZnO-TFTs can be simply fabricated at low temperature by just using a spin coating method without vacuum deposition, thus providing low manufacturing cost. Furthermore, solution based oxide TFT exhibits excellent transparency and enables to apply flexible devices. For this reason, this process has been attracting much attention as one fabrication method for oxide channel layer in thin-film transistors (TFTs). But, poor electrical characteristic of these solution based oxide materials still remains one of issuable problems due to oxygen vacancy formed by breaking weak chemical bonds during fabrication. These electrical properties are expected due to the generation of a large number of conducting carriers, resulting in huge electron scattering effect. Therefore, we study a novel technique to effectively improve the electron mobility by applying environmental annealing treatments with various gases to the solution based Li-doped ZnO TFTs. This technique was systematically designed to vary a different lithium ratio in order to confirm the electrical tendency of Li-doped ZnO TFTs. The observations of Scanning Electron Microscopy, Atomic Force Microscopy, and X-ray Photoelectron Spectroscopy were performed to investigate structural properties and elemental composition of our samples. In addition, I-V characteristics were carried out by using Keithley 4,200-Semiconductor Characterization System (4,200-SCS) with 4-probe system.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.315-315
• /
• 2016

The hydrogenated amorphous silicon (a-Si:H) thin film solar cells using n/Al or n/Ag/Al back reflector have low short circuit current (Jsc) due to high absorption coefficients of Al or work function difference between n-layer and the metal. In this article, we utilized aluminum doped zinc oxide (AZO) to raise the internal reflectance for the improvement of short current density (Jsc) in a-Si:H thin film solar cells. It was found that there was a slight increase in the reflectance in the long wavelength range at the process temperature of 125oC due to improved crystalline quality of the AZO back reflector. The optical band gap (Eg) and work function were affected by the temperature and so did the internal reflectance. The increased internal reflectance within the solar cell resulted in Jsc of 14.94 mA/cm2 and the efficiency of 8.84%. Jsc for the cell without back reflector was 12.29 mA/cm2.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.244.2-244.2
• /
• 2016

폴리 실리콘 박막은 저온 안정성, 산화 안정성, 가스 투과성 및 전기재료로서의 우수한 물성 때문에 산업에서 계속적으로 넓게 쓰이고 있다. 특히 최근 높은 색 재현율과 고화질로 각광을 받고 있는 능동형 유기발광 다이오드 (AMOLED)를 위한 Thin Film Transistor (TFT)는 신뢰성 및 우수한 특성이 요구되기 때문에 반드시 폴리실리콘 TFT가 적용되어야 한다. 이러한 이유 때문에 아모포스 실리콘을 폴리실리콘으로 결정화 시키는 방법들이 많이 연구 되어져왔다. 이 연구에서는 아모포스 실리콘 박막을 고품질의 폴리실리콘 박막으로 제조하기 위해, 기판에 positive DC 전압을 펄스 형태로 인가함으로써, 기판에 입사되는 전자를 이용한 열처리 방법을 사용하였다. 열처리 온도는 기판에 들어오는 current값을 조절함으로써 제어할 수 있었다. 열처리를 위해 사용 된 수소화 된 아모포스 실리콘은 Low Pressure Chemical Vapor Deposition (LPCVD)장비로 530도에서 증착 되었으며, 이러한 아모포스 실리콘 박막은 공정시간 60 s 이내에 샘플 표면온도가 600도 이상으로 증가함으로써 균일한 폴리실리콘 막으로 제조 되었다.

• Transactions of the Korean hydrogen and new energy society
• /
• v.7 no.1
• /
• pp.71-79
• /
• 1996

Yttrium thin film, 580nm thick, was prepared by electron beam evaporation. Film was hydrogenated room temperature upto 40 bar hydrogen pressure, without any activation process. Hydrogen concentration was determined by a quartz-crystal microbalance(QCM) method. YH2.9 sample was made without any pulverization. Electrical resistance was measured by four-point DC method in the temperature range between room temperature and 30K for various hydrogen concentration, x=0 to 2.9 of YHx sample. Temperature dependent resistance of YH2.9 shows low temperature minimum at 105K, the metal-semiconductor transition at 260K, and a hystersis above 210K.