• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.103-104
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• 2006

Transparent conductive oxide (TCO) are necessary as front electrode for increased efficiency of LED. In our paper, transparent conducting alminum-doped Zinc oxide films (AZO) were prepared by rf magnetron sputtering on glass (corning 1737) substrate, were then annealed at temperature $400^{\circ}C$ for 2hr. The smooth AZO films were etched in diluted HCL (0.5%) to examine the surface morphology properties as a variation of the time. The surface morphology of AZO films increased as a time. We observed texture structure of AZO thin film etched for 1min.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.271-275
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• 2006

Al oped zinc oxide (AZO) films were prepared by Facing Targets Sputtering (FTS) system for TCO applications. The electrical, optical and structural properties of AZO thin films have been investigated with input current, oxygen gas flow ratio and substrate temperature. Deposition was carried out at room temperature and $200^{\circ}C$. Working gas pressures were fixed at 1mTorr. As a result, AZO thin film deposited with an optical transmittance over 80 % and a resistivity about $10^{-4}{Omega}{\cdot}cm$.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.55.1-55.1
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• 2010

Cost efficient and large area deposition of superior quality $Al_2O_3$ doped zinc oxide (AZO) films is instrumental in many of its applications including solar cell fabrication due to its numerous advantages over ITO films. In this study, AZO films were prepared by a highly efficient rotating cylindrical dc magnetron sputtering system using AZO target, which has a target material utilization above 80%, on glass substrates in argon ambient. A detailed analysis on the electrical, optical and structural characteristics of AZO thin films was carried out for solar cell application. The properties of films were found to critically depend on deposition parameters such as sputtering power, substrate temperature, working pressure, and thickness of the films. A low resistivity of ${\sim}5.5{\times}10-4{\Omega}-cm$ was obtained for films deposited at 2kW, keeping the pressure and substrate temperature constant at 3 mtorr and $230^{\circ}C$ respectively, mainly due to an increase in carrier mobility and large grain size which would reduce the grain boundary scattering. The increase in carrier mobility with power can be attributed to the columnar growth of AZO film with (002) preferred orientation as revealed by XRD analysis. The AZO films showed a high transparency of>87% in the visible wavelength region irrespective of deposition conditions. Our results offers a cost-efficient AZO film deposition method which can fabricate films with significant low resistivity and high transmittance that can find application in thin-film solar cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.446-447
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• 2007

Aluminisum-doped zinc oxide (AZO) films are attractive materials as transparent conductive electrode because they are inexpensive, nontoxic and abundant element compared with indium tin oxide (ITO). In our paper, AZO films have been deposited on glass (coming 1737) substrates by RF magnetron sputtering. The AZO film was post-annealed at $600^{\circ}C$, $800^{\circ}C$ for 2 hr with $N_2$ atmosphere, respectively. We investigated that the electric properties and qualitative analysis of AZO films, which measured using the methods of Hall effect, X-ray photoelectron spectroscopy (XPS).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.280-286
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• 2010

We have investigated the influence of rapid thermal annealing (RTA) temperature on properties of Al-doped zinc oxide (AZO) thin films deposited on glass substrate by using radio-frequency magnetron sputtering. The RTA is performed in a nitrogen ambient in the temperature range from 300 to $600^{\circ}C$ for 1 minute in a rapid thermal annealer after growing the AZO thin films. The crystallographic structure and the surface morphology of AZO thin film are measured by using X-ray diffraction, and atomic force microscopy and scanning electron microscopy, respectively. The optical transmittance of the deposited thin films is examined in the wavelength range of 300-1100 nm, where the average transmittance is above the 90% in the visible and near-infrared regions. The optical bandgap is calculated from the Tauc's model, and it shows a significant dependence on the RTA temperature. As for the electrical properties of the thin films, the AZO thin film annealed at $400^{\circ}C$ shows the lowest electrical resistivity of $8.6{\times}10^{-3}{\Omega}cm$ and the Hall mobility of $11.3cm^2$/V-sec. These results suggest that the RTA temperature is an important parameter to influence on the structural, electrical, and optical properties of AZO thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.345.2-345.2
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• 2016

Alumina (Al2O3) doped zinc oxide (ZnO) films (AZO) have been prepared from 2 wt.% Al2O3 doped ZnO target by DC magnetron sputtering at a 2 mTorr (0.27 Pa) chamber pressure in (15 sccm) argon ambient. We obtained films of various opto-electronic properties by variation of target angle from 32.5o to 72.5o. At lower target angle deposited films show higher values in optical gap, mobility of charge carrier, carrier concentration, crystallite grain size, transmission range of wavelength, which are favorable characteristics of AZO as a transparent conducting oxide (TCO). At higher target angle the sheet resistance, work function, surface roughness for the AZO films increases. Measured haze ratio of the films changed lower to higher and size of characteristic surface structure of as deposited film ranges from ~40 nm to ~300 nm. By a combination of low and high target angle we obtained a textured TCO film with high conductivity.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.169-169
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• 2016

In this paper, we report electrical, optical and structural properties of Al-doped zinc oxide (AZO) thin films deposited at different substrate temperatures and pressures. The films were prepared by radio frequency (RF) magnetron sputtering on glass substrates in argon (Ar) ambient. The X-ray diffraction analysis showed that the AZO films deposited at room temperature (RT) and 20 Pa were mostly oriented along a-axis with preferred orientation along (100) direction. There was an improvement in resistivity ($3.7{\times}10^{-3}{\Omega}-cm$) transmittance (95%) at constant substrate temperature (RT) and working pressure (20 Pa) using the Hall-effect measurement system and UV-vis spectroscopy, respectively. Our results have promising applications in low-cost transparent electronics, such as the thin-film solar cells and thin-film transistors due to favourable deposition conditions. Furthermore our film deposition method offers a procedure for preparing highly oriented (100) AZO films.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.426.1-426.1
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• 2016

We report high work function Aluminum doped zinc oxide (AZO) films as insertion layer as a function of O2 flow rate between transparent conducting oxides (TCO) and hydrogenated amorphous silicon oxide (a-SiOx:H) layer to improve open circuit voltage (Voc) and fill factor (FF) for high efficiency thin film solar cell. However, amorphous silicon (a-Si:H) solar cells exhibit poor fill factors due to a Schottky barrier like impedance at the interface between a-SiOx:H windows and TCO. The impedance is caused by an increasing mismatch between the work function of TCO and that of p-type a-SiOx:H. In this study, we report on the silicon thin film solar cell by using as insertion layer of O2 reactive AZO films between TCO and p-type a-SiOx:H. Significant efficiency enhancement was demonstrated by using high work-function layers (4.95 eV at O2=2 sccm) for engineering the work function at the key interfaces to raise FF as well as Voc. Therefore, we can be obtained the conversion efficiency of 7 % at 13mA/cm2 of the current density (Jsc) and 63.35 % of FF.

• Transactions on Electrical and Electronic Materials
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• v.11 no.6
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• pp.279-284
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• 2010

This study has been carried out to determine the optimal process conditions of $AZO:H_2$ thin films for the maximization of the transmittance of a blue GaN light-emitting diode (LED) with a wavelength of 470 nm. The Al-doped zinc oxide $(AZO):H_2$ thin films were deposited on a sapphire substrate by radio-frequency magnetron sputtering system with varying substrate temperatures, working pressures and annealing temperatures temperature, working pressure and annealing imposed on a AZO (2wt% $Al_2O_3$) ceramic target. The effect of these variables was investigated in order to improve the light extraction efficiency of the LED. As a result, the (002)-oriented peak was found in all the $AZO:H_2$ thin films. The lowest resistivity and the best transmittance at a wavelength of 470 nm was found to be $4.774\;{\times}\;10^{-4}\;{\Omega}cm$ and 92% at a substrate temperature of $500^{\circ}C$, working pressure of 7 mTorr and annealing temperature of $400^{\circ}C$. The transmittance of the $AZO:H_2$ thin film for the Blue GaN LED was improved by approximately 13% relative to that of a ITO thin film (T = 79%).

• Journal of Sensor Science and Technology
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• v.22 no.2
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• pp.105-110
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• 2013

We fabricated an a-IGZO thin film transistor (TFT) with AZO/Ag/AZO transparent multilayer source/drain contacts by rf magnetron sputtering. a-IGZO TFT with AZO/Ag/AZO multilayer S/D electrodes (W/L = 400/50 ${\mu}m$) showed a subs-threshold swing of 3.78 V/dec, a minimum off-current of $10^{-12}$ A, a threshold voltage of 0.41 V, a field effect mobility of $10.86cm^2/Vs$, and an on/off ratio of $9{\times}10^9$. From the ultraviolet photoemission spectroscopy, it was revealed that the enhanced electrical performance resulted from the lowering of the Schottky barrier between a-IGZO and Ag due to the insertion of an AZO layer and thus the AZO/Ag/AZO multilayer would be very appropriate for a promising S/D contact material for the fabrication of high performance TFTs.