• Transactions on Electrical and Electronic Materials
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• 제12권1호
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• pp.11-15
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• 2011

In this study, $ZnGa_2O_4$ phosphors in its application to field emission displays and electroluminescence were synthesized through the precipitation method and $Mn^{2+}$ ions. A green luminescence activator, $Cr^{3+}$ ions, and a red luminescence activator were separately doped into $ZnGa_2O_4$, which was then screen printed to an indium tin oxide substrate. The thick films of the $ZnGa_2O_4$ were deposited with the various thicknesses using nano-sized powder. The best luminescence characteristics were shown at a thickness of 60 ${\mu}m$. Additionally, green-emission $ZnGa_2O_4:Mn^{2+}$ and red-emission $ZnGa_2O_4:Cr^{3+}$ phosphor thick films, which have superior characteristics, were manufactured through the screen-printing method. These results indicate that $ZnGa_2O_4$ phosphors prepared through the precipitation method have wide application as phosphor of the full color emission.

• 대한전자공학회논문지SD
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• 제47권1호
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• pp.6-13
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• 2010

본 연구에서는 RF 마그네트론 스퍼터링 법으로 Eagle 2000 유리 기판 위에 Ga-doped ZnO (GZO) 박막을 제작하여, 기판온도 $100{\sim}400^{\circ}C$ 및 박막두께에 따른 박막의 결정화 특성과 전기적 및 광학적 특성을 조사하였다. 공정조건에 상관없이 모든 GZO 박막은 c-축 배향성을 나타내는 (002) 회절 피크만이 관찰되었고, $300^{\circ}C$에서 400 nm 증착한 GZO 박막이 가장 우수한 결정성을 나타내었으며, 그 때의 반가폭 값은 $0.4^{\circ}$이었다. 또한, AFM 으로 박막의 표면형상을 분석한 결과 $300^{\circ}C$에서 400 nm 증착한 박막에서 비교적 입자가 고르고 치밀한 박막이 형성되었다. 전기적 특성은 홀 측정결과 $300^{\circ}C$에서 400 nm 증착한 박막에서 가장 낮은 비저항 ($8.01{\times}10^{-4}\;{\Omega}cm$)과 가장 높은 전자 캐리어농도 ($3.59{\times}10^{20}\;cm^{-3}$) 를 나타내었다. 모든 GZO 박막은 공정조건에 무관하게 가시광 영역에서 80 %의 투과율을 나타내었으며, 기판온도 및 박막두께 증가에 따른 Ga 도핑효과의 증가로 밴드 갭이 넓어지는 Burstein-Moss 효과가 관찰되었다.

• 한국재료학회지
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• 제21권3호
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• pp.144-148
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• 2011

We have investigated the structural and optical properties of Ga-doped ZnO (GZO) thin films deposited by RF magnetron sputtering at various deposition temperatures from 100 to $500^{\circ}C$. All the GZO thin films are grown as a hexagonal wurtzite phase with highly c-axis preferred parameter. The structural and electrical properties are strongly related to deposition temperature. The grain size increases with the increasing deposition temperature up to $400^{\circ}C$ and then decreases at $500^{\circ}C$. The dependence of grain size on the deposition temperature results from the variation of thermal activation energy. The resistivity of GZO thin film decreases with the increasing deposition temperature up to $300^{\circ}C$ and then decreases up to $500^{\circ}C$. GZO thin film shows the lowest resistivity of $4.3{\times}10^{-4}\;{\Omega}cm$ and highest electron concentration of $1.0{\times}10^{21}\;cm^{-3}$ at $300^{\circ}C$. The mobility of GZO thin films increases with the increasing deposition temperature up to $400^{\circ}C$ and then decreases at $500^{\circ}C$. GZO thin film shows the highest resistivity of 14.1 $cm^2/Vs$. The transmittance of GZO thin films in the visible range is above 87% at all the deposition temperatures. GZO is a feasible transparent electrode for the application to the transparent electrode of thin film solar cells.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.327-327
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• 2009

ZnO with a large band gap (~3.37 eV) and exciton binding energy (~60 meV), is suitable for optoelectronic applications such as ultraviolet (UV) light emitting diodes (LEDs) and detectors. However, the ZnO-based p-n homojunction is not readily available because it is difficult to fabricate reproducible p-type ZnO with high hall concentration and mobility. In order to solve this problem, there have been numerous attempts to develop p-n heterojunction LEDs with ZnO as the n-type layer. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducible availability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices. In particular, a number of ZnO films show UV band-edge emission with visible deep-level emission, which is originated from point defects such as oxygen vacancy, oxygen interstitial, zinc interstitial[1]. Thus, defect-related peak positions can be controlled by variation of growth or annealing conditions. In this work, the undoped ZnO film was grown on the p-GaN:Mg film using RF magnetron sputtering method. The undoped ZnO/p-GaN:Mg heterojunctions were annealed in a horizontal tube furnace. The annealing process was performed at $800^{\circ}C$ during 30 to 90 min in air ambient to observe the variation of the defect states in the ZnO film. Photoluminescence measurements were performed in order to confirm the deep-level position of the ZnO film. As a result, the deep-level emission showed orange-red color in the as-deposited film, while the defect-related peak positions of annealed films were shifted to greenish side as increasing annealing time. Furthermore, the electrical resistivity of the ZnO film was decreased after annealing process. The I-V characteristic of the LEDs showed nonlinear and rectifying behavior. The room-temperature electroluminescence (EL) was observed under forward bias. The EL showed a weak white and strong yellowish emission colors (~575 nm) in the undoped ZnO/p-GaN:Mg heterojunctions before and after annealing process, respectively.

• 한국전기전자재료학회논문지
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• 제30권6호
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• pp.372-375
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• 2017

ZnO thin films were deposited by RF magnetron sputtering and then diffused by using an As source in the ampouletube. Also, the ZnO p-n homojunction was made by using As-doped ZnO thin films, and its properties were analyzed. After the As doping, the surface roughness increased, the crystal quality deteriorated, and the full width at half maximum was increased. The As-doped ZnO thin films showed typical p-type properties, and their resistivity was as low as $2.19{\times}10^{-3}{\Omega}cm$, probably because of the in-diffusion from an external As source and out-diffusion from the GaAs substrate. Also, the ZnO p-n junction displayed the typical rectification properties of a p-n junction. Therefore, the As diffusion method is effective for obtaining ZnO films with p-type properties.

• 한국정보통신학회논문지
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• 제15권7호
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• pp.1559-1563
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• 2011

본 연구에서는 고주파 마그네트론 스퍼터링 (RF magnetron sputtering) 법으로 기판 온도 ($50{\sim}200^{\circ}C$)에 따른 GZO(Ga : 5 wt%) 박막을 PES (polyethersulfon) 플라스틱 기판위에 제작하여, 광학적 및 전기적 특성을 조사하였다. XRD 측정을 통해 공정 조건에 관계없이 모든 GZO 박막이 c축으로 우선 성장함을 확인할 수 있었다. 박막의 표면을 AFM 으로 조사한 결과, 표면 거칠기 값은 기판 온도 $200^{\circ}C$ 에서 제작한 박막에서 가장 낮은 값 (0.196 nm) 을 나타내었다. 투과도 측정 결과, GZO 박막은 약 80% 이상의 투과율을 보였고, 기판 온도가 증가할수록 에너지 밴드 갭이 증가하는 Burstein-Moss 효과를 관찰할 수 있었다. Hall 측정 결과, 기판 온도 $200^{\circ}C$에서 제작한 GZO 박막에서 가장 낮은 비저항 $6.93{\times}10-4\;{\Omega}{\cdot}cm$ 값과 가장 높은 캐리어 농도 $7.04{\times}1020/cm^3$ 값을 나타내었다.

• 한국재료학회지
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• 제21권4호
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• pp.202-206
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• 2011

We have investigated the structural and electrical properties of Ga-doped ZnO (GZO) thin films deposited by an RF magnetron sputtering at various RF powers from 50 to 90W. All the GZO thin films are grown as a hexagonal wurtzite phase with highly c-axis preferred parameters. The structural and electrical properties are strongly related to the RF power. The grain size increases as the RF power increases since the columnar growth of GZO thin film is enhanced at an elevated RF power. This result means that the crystallinity of GZO is improved as the RF power increases. The resistivity of GZO rapidly decreases as the RF power increases up to 70 W and saturates to 90W. In contrast, the electron concentration of GZO increases as the RF power increases up to 70 W and saturates to 90W. GZO thin film shows the lowest resistivity of $2.2{\times}10^{-4}{\Omega}cm$ and the highest electron concentration of $1.7{\times}10^{21}cm^{-3}$ at 90W. The mobility of GZO increases as the RF power increases since the grain boundary scattering decreases due to the reduced density of the grain boundary at a high RF power. The transmittance of GZO thin films in the visible range is above 90%. GZO is a feasible transparent electrode for application as a transparent electrode for thin film solar cells.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.9-9
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• 2009

1 wt % Ga-dope ZnO (ZnO:Ga) thin films with n-type semiconducting behavior were grown on c-sapphire substrates by radio frequency magnetron sputtering at various growth temperatures. The room temperature grown ZnO:Ga film showed the faint preferred orientation behavior along the c-axis with small domain size and high density of stacking faults, despite limited surface diffusion of the deposited atoms. The increase in the growth temperature in the range between $300\sim550^{\circ}C$ led to the granular shape of epitaxial ZnO:Ga films due to not enough thermal energy and large lattice mismatch. The growth temperature above $550^{\circ}C$ induced the quite flat surface and the simultaneous improvement of electrical carrier concentration and carrier mobility, $6.3\;\times\;10^{18}/cm^3$ and $27\;cm^2/Vs$, respectively. In addition, the increase in the grain size and the decrease in the dislocation density were observed in the high temperature grown films. The low-temperature photoluminescence of the ZnO:Ga films grown below $450^{\circ}C$ showed the redshift of deep-level emission, which was due to the transition from $Zn_j$ to $O_i$ level.

• Current Photovoltaic Research
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• 제3권1호
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• pp.32-38
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• 2015

CIGS solar cell consisted of various films. In this research, we investigated electrode materials in $Cu(In,Ga)Se_2$ (CIGS) cells, including Al-doped ZnO (ZnO:Al), intrinsic ZnO (i-ZnO), and Al films. The sputtered ZnO:Al film with a sputtering power at 200W showed the lowest series resistance and highest cell efficiency. The electrical resistivity of the 200-W sputtered ZnO:Al film was $5.2{\times}10^{-4}{\Omega}{\cdot}cm$ by the rapid thermal annealing at $200^{\circ}C$ for 1 min. The electrical resistivity of i-ZnO was not measurable due to its high resistance. But the optical transmittance was highest with less oxygen supply and high efficiency cell was achieved with $O_2/(Ar+O_2)$ ratio was 1% due to the increase of short-circuit current. No significant change in the cell performance by inserting a Ni layer between Al and ZnO:Al films was observed.