• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.8-16
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• 2010

In this paper, we investigated the effects of $O_2$ fraction on the properties of Al-doped ZnO (AZO) thin films prepared by radio frequency (RF) magnetron sputtering. Hall, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements revealed that the p-type conductivity was exhibited for AZO films with an $O_2$ fraction of 0.9 while the n-type conductivity was observed for films with $O_2$ fractions in range of 0 - 0.6. PL and XPS also showed that the acceptor-like defects, such as zinc vacancies and oxygen interstitials, increased in films prepared by an $O_2$ fraction of 0.9, resulting in the p-type conductivity in the films. Hall results indicated that AZO films prepared by $O_2$ fractions in range of 0 - 0.6 can be used for electrode layers in the applications of transparent thin film transistor. We concluded from the X-ray diffraction analysis that worse crystallinity with a smaller grain size as well as higher tensile stress was observed in the films prepared by a higher $O_2$ fraction, which is related to incorporation of more oxygen atoms into the films during deposition. The study of atomic force microscope suggested that the smoother surface morphology was observed in films prepared by using $O_2$ fraction, which causes the higher resistivity in those films, as evidenced by Hall measurements.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.181-185
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• 2005

We have investigated the effects of Al codoping on the structural, electrical transport, and magnetic properties of oxide diluted magnetic semiconductor $Zn_{1-x}Cr_xO$ thin films prepared by reactive sputtering. Nondoped $Zn_{0.99}Cr_{0.01}O$ thin films show semiconducting transport behavior and weak ferromagnetic characteristic. The Al doping increases the carrier concentration and results in an decrease of resistivity and metal-insulator transition behavior. With increasing carrier concentration, the magnetic properties drastically change, exhibiting a remarkable increase of the saturation magnetization. These results show carrier-enhanced ferromagnetic order in Cr-doped ZnO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.703-706
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• 2002

Piezoelectric thin film such as ZnO and AlN can be applicable to FBAR (Film Bulk Acoustic Resonator) device of thin film type and FBAR can be applicable to MMIC. The characteristic of FBAR device is variable according to the deposition conditions of piezoelectric thin film when preparation of thin film by sputtering method. In this study, we prepared ZnO thin film for FBAR using Facing Targets Sputtering apparatus which can be deposited fine Quality thin film because temperature increase of substrate due to the bombardment of high-energy particles can be restrained. And crystalline and c-axis preferred orientation of ZnO thin film with deposition conditions was investigated by XRD.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.164-164
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• 2010

The impurity doped ZnO has been extensively studied because of its optoelectric properties. GIZO (Ga-In-Zn-O) amorphous oxide semiconductors has been widely used as transparent flexible semiconductor material. Recently, various amorphous transparent semiconductors such as IZO (In-Zn-O), GIZO, and HIZO (Hf-In-Zn-O) were developed. In this work, we examined the local structures of IZO, GIZO, and HIZO. The local coordination structure was investigated by the extended X-ray absorption fine structure. The IZO, GIZO and HIZO thin films ware deposited on the glass substrate with thickness of 400nm by the radio frequency sputtering method. The targets were prepared by the mixture of $In_2O_3$, ZnO and $HfO_2$ powders. The percent ratio of In:Zn in IZO, Ga:In:Zn in GIZO and Hf:In:Zn in HIZO was 45:55, 33:33:33 and 10:35:55, respectively. In this work, we found that IZO, GIZO and HIZO are all amorphous and have a similar local structure. Also, we obtained the bond distances of $d_{Ga-O}=1.85\;{\AA}$, $d_{Zn-O}=1.98\;{\AA}$, $d_{Hf-O}=2.08\;{\AA}$, $d_{In-O}=2.13\;{\AA}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.510-513
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• 2003

Our Zn diffusion into n-type $GaAs_{0.40}P_{0.60}$ used ampoule-tube method to increase IV. N-type epitaxial wafers were preferred by $H_2SO_4$-based pre-treatment. $SiO_2$ thin film was deposited by PECVD for some wafers. Diffusion times and diffusion temperatures respectability are 1, 2, 3 hr and 775, $805^{\circ}C$. LED chips were fabricated by the diffused wafers at Fab. The peak wavelength of all chips showed about $625{\sim}650\;nm$ and red color. The highest IV is about 270 mcd at the diffusion condition of $775^{\circ}C$, 3h for the wafers which didn't deposit $SiO_2$ thin films. Also, the longer diffusion time is the higher IV for the wafers which deposit $SiO_2$ thin films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.883-888
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• 2007

Investigation of improving the properties of UV detector which uses the wide bandgap of ZnO are under active progress. The present study focused on the design and fabrication of i-ZnO/p-inversion $layer/n^--Si$ Epi. which is characterized with very thin p-type inversion layer for UV detectors. The i-ZnO thin film for achieving p-inversion layer which was grown by RF sputtering at $450^{\circ}C$ and then annealed at $400^{\circ}C$ in $O_2$ gas for 20 min shows good intrinsic properties. High (0002) peak intensity of the i-ZnO film is shown on XRD spectrum and it is confirmed by XPS analysis that the ratio of Zn : O of the i-ZnO film is nearly 1 : 1. Measurement shows high transmission of 79.5 % in UV range (< 400 nm) for the i-ZnO film. Measurement of $V_r-I_{ph}$ shows high UV photo-current of 1.2 mA under the reverse bias of 30 V.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.174-174
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• 2003

ZnO는 상온에서 3.36 eV의 wide band gap과 60 meV의 큰 엑시톤 결합 에너지를 가지며, GaN(28 meV)와 ZnSe(19 meV)와 같은 wide band gap 재료와 비교해서 가장 우수한 exciton emission을 가진다. 이러한 특성 때문에 UV 레이저 및 LED와 같은 광학소자로서 그 응용의 잠재성이 높다. 박막의 우수한 광학적 특성과 결정성을 개선하기 위해 다양한 공정조건(RF 파워, 공정압력, 산소분압, 온도)에서 마그네트론 스퍼터링을 이웅하여 Si 기판상에 ZnO 박막을 성장 하였다. 또한, 저온 self-buffer를 이용하여 박막의 광학적 특성과 결정성을 더욱 개선 할 수 있었다. RF 파워와 공정압력은 박막의 PL(phothluminescehce) 특성이나 결정성에는 큰 영향을 주지 않았고 산소분압은 PL intensity의 변화를 가져왔으며, 온도는 결정성에 큰 영향을 주었다. 산소 분압이 증가 할수록 비화학량론적(산소 공공, 침입형 아연) 결함으로 인한 visiable 영 역의 peak 의 강도가 감소하는 것을 관찰하였다. 온도가 증가할수록 박막의 결정성에 나쁜 영향을 주었는데 저온 self-buffer를 도입하므로써 ZnO 박막의 결정성과 PL특성을 함께 개선하였다.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.72-74
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• 2003

Rf magnetron sputtering을 이용하여 InP, GaAs 기판위에 ZnO 박막을 증착시켰다. 진공 ampul 및 $Zn_3P_2$ 분위기 하에서 열처리 과정을 통해 P와 As을 ZnO 박막내에 도핑하였으며, 박막의 전기적 특성 측정 결과 정공의 농도가 $10^{16}cm^{-3}-10^{19}cm^{-3}$ 으로서 p-형 전기전도도를 나타내었다. XRD 측정을 통하여 ZnO 박막의 내부에 이상이 존재하지 않는다는 것을 확인하였다. 또한 FESEM을 이용하여 p-형 ZnO 박막의 표면을 관찰하였으며 그 위에 n-형 ZnO 박막을 sputtering을 이용하여 증착시켜 I-V 특성을 관찰하였다. 본 실험을 통해 P 및 As의 확산을 통한 p-형 ZnO 박막의 성장이 가능하였으며, I-V 특성으로부터 ZnO의 발광소자 및 자외선 검출기로의 응용이 가능함을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.154-159
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• 2005

Low RF power density was used for preparing transparent conducting AI-doped ZnO (AZO) thin films by RF Magnetron Sputtering on Corning 1737 glass. The dependence of films' structural, optical and electrical properties on sputtering gas, film's thickness and substrate temperature were investigated. Low percent of incorporated H2 in Ar sputtering gas has proven to reduce film's resistivity and sheet resistance as low as $4.1\times10^{-3}{\Omega}.cm$. It also formed new preferred peaks orientation of (101) and (100) which indicated that the c-axis of AZO films was parallel to the substrate. From UN-VIS-NIR Spectrophotometer analysis, it further showed high optical transmittance at about $\~ 90\%$ at visible light spectra (400-700nm).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.95-96
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• 2005

The general method and mechanism for the polarity control of heteroepitaxial wurtzite films, such as ZnO and GaN, by interface engineering via plasma-assisted molecular beam epitaxy are addressed. We proposed the principle and method controlling the crystal polarity of ZnO on GaN and GaN on ZnO. The crystal polarity of the lower film was maintained by forming a heterointerfce without any interface layer between the upper and the lower layers. However the crystal polarity could be changed by forming the heterointerface with the interface layer having an inversion center. The principle and method suggested here give us a promising tool to fabricate polarity inverted heterostructures, which applicable to invent novel heterostructures and devices.