• Bulletin of the Korean Chemical Society
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• v.16 no.5
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• pp.416-421
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• 1995

The approximate rates and stoichiometry of the reaction of excess lithium gallium hydride with selected organic compounds containing representative functional groups were examined under the standard conditions (diethyl ether, 0 $^{\circ}C)$ in order to compare its reducing characteristics with lithium aluminum hydride and lithium borohydride previously reported, and enlarge the scope of its applicability as a reducing agent. Alcohols, phenol, and amines evolve hydrogen rapidly and quantitatively. However lithium gallium hydride reacts with only one active hydrogen of primary amine. Aldehydes and ketones of diverse structure are rapidly reduced to the corresponding alcohols. Conjugated aldehyde and ketone such as cinnamaldehyde and methyl vinyl ketone are rapidly reduced to the corresponding saturated alcohols. p-Benzoquinone is mainly reduces to hydroquinone. Caproic acid and benzoic acid liberate hydrogen rapidly and quantitatively, but reduction proceeds slowly. The acid chlorides and esters tested are all rapidly reduced to the corresponding alcohols. Alkyl halides and epoxides are reduced rapidly with an uptake of 1 equiv of hydride. Styrene oxide is reduced to give 1-phenylethanol quantitatively. Primary amides are reduced slowly. Benzonitrile consumes 2.0 equiv of hydride rapidly, whereas capronitrile is reduced slowly. Nitro compounds consumed 2.9 equiv of hydride, of which 1.9 equiv is for reduction, whereas azobenzene, and azoxybenzene are inert toward this reagent. Cyclohexanone oxime is reduced consuming 2.0 equiv of hydride for reduction at a moderate rate. Pyridine is inert toward this reagent. Disulfides and sulfoxides are reduced slowly, whereas sulfide, sulfone, and sulfonate are inert under these reaction conditions. Sulfonic acid evolves 1 equiv of hydrogen instantly, but reduction is not proceeded.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.12-23
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• 2018

In this paper, we review the technical trends of diamond and gallium oxide ($Ga_2O_3$) semiconductor technologies among ultra-wide bandgap semiconductor technologies for harsh environments. Diamond exhibits some of the most extreme physical properties such as a wide bandgap, high breakdown field, high electron mobility, and high thermal conductivity, yet its practical use in harsh environments has been limited owing to its scarcity, expense, and small-sized substrate. In addition, the difficulty of n-type doping through ion implantation into diamond is an obstacle to the normally-off operation of transistors. $Ga_2O_3$ also has material properties such as a wide bandgap, high breakdown field, and high working temperature superior to that of silicon, gallium arsenide, gallium nitride, silicon carbide, and so on. In addition, $Ga_2O_3$ bulk crystal growth has developed dramatically. Although the bulk growth is still relatively immature, a 2-inch substrate can already be purchased, whereas 4- and 6-inch substrates are currently under development. Owing to the rapid development of $Ga_2O_3$ bulk and epitaxy growth, device results have quickly followed. We look briefly into diamond and $Ga_2O_3$ semiconductor devices and epitaxy results that can be applied to harsh environments.

• Transactions on Electrical and Electronic Materials
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• v.17 no.3
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• pp.143-145
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• 2016

In order to find suitable source and drain (S/D) electrodes for amorphous InGaZnO thin film transistors (a-IGZO TFTs), the specific contact resistance of interface between the channel layers and various S/D electrodes, such as Ti/Au, a-IZO and multilayer of a-IGZO/Ag/a-IGZO, was investigated using the transmission line model. The a-IGZO TFTs with a-IGZO/Ag/a-IGZO of S/D electrodes had good performance and low contact resistance due to the homo-junction with channel layer. The stability was measured with different electrodes by a positive bias stress test. The result shows the a-IGZO TFTs with a-IGZO/Ag/a-IGZO electrodes were more stable than other devices.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.119-122
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• 2008

In this paper, we describe the current status and issues of the oxide thin-film transistors (OTFTs), which attract much attention as an emerging new backplane technology replacing conventional silicon-based TFTs technologies. First, the unique benefits of OTFTs will be presented as a backplane for large-sized AMOLED including note-book PC, second TV and HD-TV. And then, the state-of-the-art transistor performance and uniformity characteristics of OTFTs will be highlighted. The obtained a-IGZO TFTs exhibited the field-effect mobility of $18\;cm^2/Vs$, threshold voltage of 1.8 V, on/off ratio of $10^9$, and subthreshold gate swing of 0.28 V/decade. In addition, the world largest-sized 12.1-inch WXGA active-matrix organic light emitting diode (AMOLED) display is demonstrated using indium-gallium-zinc oxide (IGZO) TFTs.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1489-1498
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• 2015

Gallium nitride (GaN)-based power switching devices, such as high-electron-mobility transistors (HEMT), provide significant performance improvements in terms of faster switching speed, zero reverse recovery, and lower on-state resistance compared with conventional silicon (Si) metal-oxide-semiconductor field-effect transistors (MOSFET). These benefits of GaN HEMTs further lead to low loss, high switching frequency, and high power density converters. Through simulation and experimentation, this research thoroughly contributes to the understanding of performance characterization including the efficiency, loss distribution, and thermal behavior of a 160-W GaN-based synchronous boost converter under various output voltage, load current, and switching frequency operations, as compared with the state-of-the-art Si technology. Original suggestions on design considerations to optimize the GaN converter performance are also provided.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.33-37
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• 2014

We have developed a novel passivation process employing a sacrificial gallium oxide process in order to recover the surface damage in AlGaN/GaN HFETs. Even with a conventional prepassivation process, surface damage during high temperature ohmic annealing cannot be avoided completely. Therefore, it is necessary to recover the damaged surface to avoid the characteristic degradation. In this work, a sacrificial gallium oxide process has been proposed in which the damaged surface after ohmic annealing was oxidized by oxygen plasma treatment and thereafter etched back using HCl. As a result, the leakage current was dramatically reduced and thus the subthreshold slope was significantly improved. In addition, the maximum drain current level was increased from 594 to 634 mA/mm. To verify the effects, the surface conditions were carefully investigated using X-ray photoelectron spectroscopy.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.352.1-352.1
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• 2014

Indium Tin Oxide (ITO) films are the most extensively studied and commonly used as ones of TCO films. The ITO films having a high electric conductivity and high transparency are easily fabricated on glass substrate at a substrate temperature over $250^{\circ}C$. However, glass substrates are somewhat heavy and brittle, whereas plastic substrates are lightweight, unbreakable, and so on. For these reasons, it has been recently suggested to use plastic substrates for flexible display application instead of glass. Many reaearchers have tried to produce high quality thin films at rood temperatures by using several methods. Therefore, amorphous ITO films excluding thermal process exhibit a decrease in electrical conductivity and optical transparency with time and a very poor chemical stability. However the amorphous Indium Gallium Zinc Oxide (IGZO) offers several advantages. For typical instance, unlike either crystalline or amorphous ITO, same and higher than a-IGZO resistivity is found when no reactive oxygen is added to the sputter chamber, this greatly simplifies the deposition. We reported on the characteristics of a-IGZO thin films were fabricated by RF-magnetron sputtering method on the PEN substrate at room temperature using 3inch sputtering targets different rate of Zn. The homogeneous and stable targets were prepared by calcine and sintering process. Furthermore, two types of IGZO TFT design, a- IGZO source/drain material in TFT and the other a- ITO source/drain material, have been fabricated for comparison with each other. The experimental results reveal that the a- IGZO source/drain electrode in IGZO TFT is shown to be superior TFT performances, compared with a- ITO source/drain electrode in IGZO TFT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.8-8
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• 2009

Thin-film transistors (TFTs) were fabricated using amorphous indium gallium zinc oxide (a-IGZO) channels by rf-magnetron sputtering at room temperature. We have studied the effect of oxygen partial pressure on the threshold voltage($V_{th}$) of a-IGZO TFTs. Interestingly, the $V_{th}$ value of the oxide TFTs are slightly shifted in the positive direction due to increasing $O_2$ ratio from 1.2 to 1.8%. The device performance is significantly affected by varying $O_2$ ratio, which is closely related with oxygen vacancies provide the needed free carriers for electrical conduction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.10
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• pp.648-652
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• 2014

We have investigated the effect of electrical properties of amorphous InGaZnO thin film transistors (a-IGZO TFTs) by post thermal annealing in $O_2$ ambient. The post-annealed in $O_2$ ambient a-IGZOTFT is found to be more stable to be used for oxide-based TFT devices, and has better performance, such as the on/off current ratios, sub-threshold voltage gate swing, and, as well as reasonable threshold voltage, than others do. The interface trap density is controlled to achieve the optimum value of TFT transfer and output characteristics. The device performance is significantly affected by adjusting the annealing condition. This effect is closely related with the modulation annealing method by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.

• Journal of Information Display
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• v.11 no.4
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• pp.165-168
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• 2010

A solution-processed multicomponent oxide, yttrium hafnium zinc oxide (YHZO), was synthesized and deposited as a gate insulator. The YHZO film annealed at $600^{\circ}C$ contained an amorphous phase based on the results of thermogravimetry, differential thermal analysis, and X-ray diffraction. The electrical characteristics of the YHZO film were analyzed by measuring the leakage current. The high dielectric constant (16.4) and high breakdown voltage (71.6 V) of the YHZO films resulted from the characteristics of $HfO_2$ and $Y_2O_3$, respectively. To examine if YHZO can be applied to thin-film transistors (TFTs), indium gallium zinc oxide TFTs with a YHZO gate insulator were also fabricated. The desirable characteristics of the YHZO films when used as a gate insulator show that the limitations of the general binary-oxide-based materials and of the conventional vacuum processes can be overcome.