• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.385-390
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• 2013

$(Ga_2O_3)_x(ZnO)_{100-x}$ (GZO) films were prepared at room temperature by using a facing target sputtering (FTS) system and their electrical resistivites was investigated as a function of the $Ga_2O_3$ content. The GZO film with an atomic ratio of $Ga_2O_3$ of x= 7 wt.%, shows the lowest resistivity of $7.5{\times}10^{-4}{\Omega}{\cdot}cm$. The GZO films were also prepared at various substrate temperatures from room temperature to $300^{\circ}C$, and their electrical resistivity was found to be improved as the substrate temperature was increased, A very low resistivity of $2.8{\times}10^{-4}{\Omega}{\cdot}cm$ that is almost comparable with that of ITO film was obtained in the GZO films prepared at the substrate temperature of $300^{\circ}C$ by using the FTS.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.685-690
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• 2010

ZnO with the wide band gap near 3.37 eV is typically an n-type semiconductor in which deviation from stoichiometry is electrically active. It was known that the films with a resistivity of the order of $10^{-4}{\Omega}cm$ is not easy to obtain. In order to improve electrical characteristic of ZnO, we added 1, 3, 5 wt% Ga element in ZnO. The Ga-doped ZnO (GZO) was grown on a glass substrate by radio frequency (RF) magnetron sputtering at the temperature range from 100 to $500^{\circ}C$. X-ray diffraction (XRD) patterns of GZO films showed preferable crystal orientation of (002) plane. The lowest resistivity of the GZO films was $8.9{\times}10^{-4}{\Omega}cm$. GZO films significantly influenced by the working temperature. The average transmittance of the films was over 80% in the visible ranges.

• 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 Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.145-146
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• 2006

The most Important research topic in the development of ZnO LED and LD is the production of p-type ZnO thin film that has minimal stress with outstanding stoichiometric ratio. In this study, Phosphorus diffused into the undoped ZnO thin films using the ampoule-tube method for the production of p-type znO thin films. The undoped ZnO thin films were deposited by RF magnetron sputtering system on $GaAs_{0.6}P_{0.4}$/GaP and Si wafers. 4N Phosphorus (P) was diffused into the undoped ZnO thin films in ampoule-tube which was performed and $630^{\circ}C$ during 3hr. We found the diffusion condition of the conductive ZnO films which had p-type properties with the highest mobility of above 532 $cm^2$/Vs compared with other studies PL spectra measured at 10K for the purpose of analyzing optical properties of p-type ZnO thin film showed strong PL intensity in the UV emission band around 365nm ~ 415nm and 365nm ~ 385nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.434-436
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• 2013

Ga-doped ZnO (GZO) was substitutes of the SnO2:F films on soda lime glass substrate in the photovoltaic devices such as CIGS, CdTe and DSSC due to good properties and low cost. However, it was reported that the electrical resistivity of GZO is unstable above $300^{\circ}C$ in air atmosphere. To improve thermal stability of GZO thin films at high temperature above $300^{\circ}C$ an $TiO_2$ thin film was deposited on the top of GZO thin films as a barrier layer by Pulsed Laser Deposition (PLD) method. $TiO_2$ thin films were deposited at various thicknesses from 25 nm to 100 nm. Subsequently, these films were annealed at temperature of $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$ in air atmosphere for 20 min. The XRD measurement results showed all the films had a preferentially oriented ( 0 0 2 ) peak, and the intensity of ( 0 0 2 ) peak nearly did not change both GZO (300 nm) single layer and $TiO_2$ (50 nm)/GZO (300 nm) double layer. The resistivity of GZO (300 nm) single layer increased from $7.6{\times}10^{-4}{\Omega}m$ (RT) to $7.7{\times}10^{-2}{\Omega}m$ ($500^{\circ}C$). However, in the case of the $TiO_2$ (50 nm)/GZO (300 nm) double layer, resistivity showed small change from $7.9{\times}10^{-4}{\Omega}m$ (RT) to $5.2{\times}10^{-3}{\Omega}m$ ($500^{\circ}C$). Meanwhile, the average transmittance of all the films exceeded 80% in the visible spectrum, which suggests that these films will be suitable for photovoltaic devices.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.175-175
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• 2009

AZO, GZO, ZIO 박막은 DC 마그네트론 법으로 각각의 소결체 타겟을 사용하여 유리 기판위에 증착되었다. 상온에서 증착된 GZO 박막의 경우 $1.61{\times}10^{-3}{\Omega}cm$ 의 가장 낮은 비저항을 나타내었다. 전기적 특성을 향상시키기 위하여 기판온도를 상승하였을 때 역시 GZO 박막이 가장 낮은 $6.413{\times}10^{-4}{\Omega}cm$ 을 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.11-11
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• 2008

ZnO has a very large exciton binding energy (60 meV) as well as thermal and chemical stability, which are expected to allow efficient excitonic emission, even at room temperature. ZnO based electronic devices have attracted increasing interest as the backplanes for applications in the next-generation displays, such as active-matrix liquid crystal displays (AMLCDs) and active-matrix organic light emitting diodes (AMOLEDs), and in solid state lighting systems as a substitution for GaN based light emitting diodes (LEDs). Most of these electronic devices employ the electrical behavior of n-type semiconducting active oxides due to the difficulty in obtaining a p-type film with long-term stability and high performance. p-type ZnO films can be produced by substituting group V elements (N, P, and As) for the O sites or group I elements (Li, Na, and K) for Zn sites. However, the achievement of p-type ZnO is a difficult task due to self-compensation induced from intrinsic donor defects, such as O vacancies (Vo) and Zn interstitials ($Zn_i$), or an unintentional extrinsic donor such as H. Phosphorus (P) doped ZnO thin films were grown on c-sapphire substrates by radio frequency magnetron sputtering with various Ar/ $O_2$ gas ratios. Control of the electrical types in the P-doped ZnO films was achieved by varying the gas ratio with out post-annealing. The P-doped ZnO films grown at a Ar/ $O_2$ ratio of 3/1 showed p-type conductivity with a hole concentration and hole mobility of $10^{-17}cm^{-3}$ and $2.5cm^2/V{\cdot}s$, respectively. X-ray diffraction showed that the ZnO (0002) peak shifted to lower angle due to the positioning of $p^{3-}$ ions with a smaller ionic radius in the $O^{2-}$ sites. This indicates that a p-type mechanism was due to the substitutional Po. The low-temperature photoluminescence of the p-type ZnO films showed p-type related neutral acceptor-bound exciton emission. The p-ZnO/n-Si heterojunction LEO showed typical rectification behavior, which confirmed the p-type characteristics of the ZnO films in the as-deposited status, despite the deep-level related electroluminescence emission.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.6
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• pp.338-342
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• 2011

Ga doped ZnO (GZO) thin films were deposited with RF magnetron sputtering on glass substrate and then the effect of post deposition annealing at nitrogen atmosphere on the structural, optical and electrical properties of the films was investigated. The post deposition annealing process was conducted for 30 minutes at different temperature of 150, 300 and $450^{\circ}C$, respectively. As increase annealing temperature, GZO films show the increment of the prefer orientation of ZnO (002) diffraction peak in the XRD pattern and the optical transmittance in a visible wave region was also increased, while the electrical sheet resistance was decreased. The figure of merit obtained in this study means that GZO films which vacuum annealed at $450^{\circ}C$ have the highest optoelectrical performance in this study.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.59-59
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• 2010

ZnO는 II-VI 족 화합물 반도체로써 상온에서 큰 엑시톤 결합에너지 (~60 meV) 를 가지며 밴드갭이 3.37 eV인 직접 천이형 반도체로 잘 알려진 물질이다. 이러한 ZnO의 물리적 특성은 광학소자로 상용화된 GaN와 유사하기 때문에 LED나 LD등의 광 소자 재료로 주목 받고 있다. 또한 ZnO는 3족 원소 (In, Ga, Al)를 도핑 함으로써 전기적 특성 제어가 가능한 장점을 가지고 있다. 본 연구는 펄스레이저 증착법 (Pulsed Laser Deposition)을 이용하여 Si (111) 기판 위에 ZnO:In 박막을 성장 시켰으며, 도핑된 indium 양에 따른 ZnO 박막의 배향성 변화를 관찰 하였다. X-선 회절 분석법 (X-ray diffraction), 탐침형 원자현미경 (Atomic Force Microscope) 그리고 투과전자 현미경 (Transmission Electron Microscope)을 측정하였다. XRD 측정 결과 un-doped ZnO 박막은 (002) 방향으로 c-축 우선성장 하였다. 그러나 ZnO 박막내의 Indium 양이 증가 할수록 (002) 방향에서 (101), (102), (103) 등의 (101) 방향으로 성장이 변화 하였으며 5 at.% 이상에서는 (100) 방향의 성장이 관찰 되었다. TEM 측정 결과 un-doped ZnO 박막은 columnar 구조로 성장 되었으나, Indium 양이 증가할수록 column의 size가 감소하며, 5 at.% 이상에서 columnar 구조 성장이 거의 관찰되지 않는다. AFM 결과에서는 Indium 양이 증가 할수록 박막의 표면거칠기와 결정립 크기가 감소하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.6
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• pp.491-496
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• 2011

Al-doped ZnO film on glass substrate is deposited by ALD in low temperature, using 4-step process (DEZ-$H_2O$-TMA-$H_2O$). To find out the optimal film condition for TCO material, we fabricate Al-doped ZnO films by increasing Al doping concentration at $100^{\circ}C$, so that the Al-doped film of 5 at% shows the lowest resistivity ($1.057{\times}10^{-2}{\Omega}{\cdot}cm$) and the largest grain size (38.047 nm). Afterwards, the electrical and physical characteristics in Al-doped films of 5 at% are also compared in accordance with increasing deposition temperature. All the films show the optical transmittance over 80% and the film deposited at $250^{\circ}C$ demonstrates the superior resistivity ($1.237{\times}10^{-4}{\Omega}{\cdot}cm$).