• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.146-147
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• 2008

In this paper we report upon an investigation into the effect of sputter RF power on the electrical properties of Gallium doped zinc oxide (ZnO:Ga) film. Structural, electrical and optical properties of the ZnO:Ga films were investigation in terms of the sputtering power. Working pressure fixed in 5 mtorr and RF powers the variable did with 50~100 W. The result, We were able to without substrate temperature obtain resistivity of $9.3\times10^{-4}{\Omega}cm$ and optical transmittance of 90%.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.207-207
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• 2010

Both ZnO and GaN have excellent physical properties in optoelectronic devices such as blue light emitting diode (LED), blue laser diode (LD), and ultra-violet (UV) detector. The ZnO/GaN heterostructure, which has a potential to achieve the cost efficient LED technology, has been fabricated by using radio frequency (RF) sputtering, pyrolysis, metal organic chemical vapor deposition (MOCVD), direct current (DC) arc plasmatron, and pulsed laser deposition (PLD) methods. Among them, the PLD system has a benefit to control the composition ratio of the grown film from the mixture target. A 500-nm-thick ZnO film was grown by PLD technique on c-plane GaN/sapphire substrates. The post annealing process was executed at some varied temperature between from $300^{\circ}C$ to $900^{\circ}C$. The morphology and crystal structural properties obtained by using atomic force microscope (AFM) and x-ray diffraction (XRD) showed that the crystal quality of ZnO thin films can be improved as increasing the annealing temperature. We will discuss the post-treatment effect on film quality (uniformity and reliability) of ZnO/GaN heterostructures.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.38-39
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• 2003

전기적 저항이 낮은 투명 박막 물질은 현재 flat panel display, electroluminescent device, thin film transistor, solar cell 등 여러 분야에서 연구되고 있다. 그 중에서도 특히 ZnO：Ga는 현재 많이 쓰이는 ITO보다 화학적, 열적으로 안정한 상태를 보이는 투명 전도 산화막 물질로써 본 연구에서는 분광타원법을 이용하여 ZnO：Ga의 광학적 특성을 분석하였다. 본 연구를 위한 시료는 온도에 따른 ZnO：Ga／Sapphire 박막, $O_2$의 압력에 따른 ZnO：Ga／Sapphire 박막, Ga의 doping 농도에 따른 ZnO：Ga／Sapphire 박막으로 제작하였으며, 위상변조형 분광타원계(spectroscopic Phase Modulated Ellipsometer, Jobin-Yvon, UVISEL)를 사용하여 측정대역을 0.74 ~ 4.5 eV, 입사각을 70$^{\circ}$로 하여 측정하였다. (중략)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.4
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• pp.289-293
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• 2013

We have studied structural, optical, and electrical properties of the Ga-doped ZnO (GZO) thin films being usable in transparent conducting oxides. The GZO thin films were deposited on the corning 1737 glass plate by the RF magnetron sputtering system. To find optimal properties of GZO for transparent conducting oxides, the Ar gas in sputtering process was varied as 40, 60, 80 and 100 sccm, respectively. As reaction gas decreased, the crystallinity of GZO thin film was increased, the optical bandgap of GZO thin film increased. The transmittance of the film was over 80% in the visible light range regardless of the changes in reaction gas. The measurement of Hall effect characterizes the whole thin film as n-type, and the electrical property was improved with decreasing reaction gas. The structural, optical, and electrical properties of the GZO thin films were affected by Ga dopant content in GZO thin film.

• Current Photovoltaic Research
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• v.5 no.4
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• pp.135-139
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• 2017

We fabricated two different transparent conducting oxide thin films of ZnO doped with Ga ($Ga_2O_3$ 0.9 wt%) as well as Al ($Al_2O_3$ 2.1 wt%) (GAZO) and ZnO doped only with Al ($Al_2O_3$ 3 wt%) (AZO). It was investigated how it affects the moisture resistance of the transparent electrode. In addition, $Cu(In,Ga)Se_2$ thin film solar cells with two transparent oxides as front electrodes were fabricated, and the correlation between humidity resistance of transparent electrodes and device performance of solar cells was examined. When both transparent electrodes were exposed to high temperature distilled water, they showed a rapid increase in sheet resistance and a decrease in the fill factor of the solar cell. However, AZO showed a drastic decrease in efficiency at the beginning of exposure, while GAZO showed that the deterioration of efficiency occurred over a long period of time and that the long term moisture resistance of GAZO was better.

• Journal of the Semiconductor & Display Technology
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• v.9 no.3
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• pp.41-45
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• 2010

The ZnO thin films doped with Ga(GZO) and both Ga and Ge(GZO:Ge) were deposited on glass substrate by using RF sputtering system respectively. Structural, morphological and optical properties of the films deposited in the same condition were investigated. Structural properties of the films were investigated by Field Emission Scanning Electron Microscopy, FE-SEM images and X-ray diffraction, XRD analysis. These studies showed shape of films' surface and direction of film growth respectively. It's showed that all films were deposited by vertical orientation strongly. It can be confirmed that all dopants of targets were included in deposited films by results of EDX analysis. UV-Vis spectrometer results showed that all samples had highly transparent characteristics in visible region and have similar 3.28~3.31 eV band gap. It was found that existence of all dopants by EDX analysis. Morphology and roughness of surface of each film were clearly shown by Atomic Force Microscopy, AFM images. It was found in this research that film doped with Ge more dense and stable with hardly any difference in gap energy compared to ZnO films.

• Current Photovoltaic Research
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• v.5 no.1
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• pp.28-32
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• 2017

In this paper, (Ga,Al):ZnO layers were deposited by sputtering to evaluate the device performance according to the thickness of the layer. As the thickness increased, low transmittance was observed, but the electrical resistance was improved. On the other hand, the highest efficiency was recorded at 400 nm device than a 500 nm of it. Therefore, since the critical thickness exists, it is necessary to set an adequate TCO layer thickness in consideration of the characteristics of the underlying film and the device.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.693-694
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• 2010

• Advances in nano research
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• v.5 no.3
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• pp.193-201
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• 2017

ZnO, ZnO: Cu, Ga, and ZnO: Cu, Ga, Ag thin films were obtained by oxidization of ZnS and ZnS: Cu, Ga films deposited onto glass substrates by electron-beam evaporation from ZnS and ZnS: Cu, Ga targets and from ZnS: Cu, Ga film additionally doped with Ag by the closed space sublimation technique at atmospheric pressure. The film thickness was about $1{\mu}m$. The oxidation was carried out at $600-650^{\circ}C$ in air or in an atmosphere containing water vapor. Structural characteristics were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). Photoluminescence (PL) spectra of the films were measured at 30-300 K using the excitation wavelengths of 337, 405 and 457.9 nm. As-deposited ZnS and ZnS: Cu, Ga films had cubic structure. The oxidation of the doped films in air or in water vapors led to complete ZnO phase transition. XRD and AFM studies showed that the grain sizes of oxidized films at wet annealing were larger than of the films after dry annealing. As-deposited doped and undoped ZnS thin films did not emit PL. Shape and intensity of the PL emission depended on doping and oxidation conditions. Emission intensity of the films annealed in water vapors was higher than of the films annealed in the air. PL of ZnO: Cu, Ga films excited by 337 nm wavelength exhibits UV (380 nm) and green emission (500 nm). PL spectra at 300 and 30 K excited by 457.9 and 405 nm wavelengths consisted of two bands - the green band at 500 nm and the red band at 650 nm. Location and intensities ratio depended on the preparation conditions.

• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.332-335
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• 2020

Drop casting, a solution process, is a simple low-cost fabrication technique that does not waste material. In this study, we elucidate the effect of the concentration of a InGaZnO solution on the electrical properties of drop-cast oxide thin-film transistors. The higher the concentration the larger the amount of remnant InGaZnO solutes, which yields a thicker thin film. Accordingly, the electrical properties were strongly dependent on the concentration. At a high concentration of 0.3 M (or higher), a large current flowed but did not lead to switching characteristics. At a concentration lower than 0.01 M, switching characteristics were observed, but the mobility was small. In addition to a high mobility, sufficient switching characteristics were obtained at a concentration of 0.1 M owing to the appropriate thickness of the semiconductor layer. This study provides a technical basis for the low-cost fabrication of switching devices capable of driving a sensor array.