• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1057-1061
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• 2007

In this study, we investigated the properties of ZnO thin films prepared by layer-by-layer method in RF magnetron sputtering system using AlAs and ZnO targets. Effects of $H_2O_2$ dip prior to thermal treatment were studied as well. Either n-type or p-type films were observed in our study depending on the annealing conditions. It thus indicates the feasibility of arbitrarily modifying the conductivity type. At the same time, it also implies the thermal instabilities of the film properties. Property measurements after stressing the films up to 144 hours showed that thermal variations of properties nay be suppressed by pre-treatment in 30% $H_2O_2$ for 1 min.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.347-352
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• 2016

ZnO with wurtzite structure has a wide band gap of 3.37 eV. Because ZnO has a direct band gap and a large exciton binding energy, it has higher optical efficiency and thermal stability than the GaN material of blue light emitting devices. To fabricate ZnO devices with optical and thermal advantages, n-type and p-type doping are needed. Many research groups have devoted themselves to fabricating stable p-type ZnO. In this study, $As^+$ ion was implanted using an ion implanter to fabricate p-type ZnO. After the ion implant, rapid thermal annealing (RTA) was conducted to activate the arsenic dopants. First, the structural and optical properties of the ZnO thin films were investigated for as-grown, as-implanted, and annealed ZnO using FE-SEM, XRD, and PL, respectively. Then, the structural, optical, and electrical properties of the ZnO thin films, depending on the As ion dose variation and the RTA temperatures, were analyzed using the same methods. In our experiment, p-type ZnO thin films with a hole concentration of $1.263{\times}10^{18}cm^{-3}$ were obtained when the dose of $5{\times}10^{14}$ As $ions/cm^2$ was implanted and the RTA was conducted at $850^{\circ}C$ for 1 min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.414-414
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• 2008

Vertically well-aligned Ga-doped ZnO nanorods with different Ga contents were grown by thermal evaporation on a ZnO template. The Ga-doped ZnO nanorods synthesized with 50 wt % Ga with respect to the Zn content showed maximum compressive stress relative to the ZnO template, which led to a rapid growth rate along the c-axis due to the rapid release of stored strain energy. A further increase in the Ga content improved the conductivity of the nanorods due to the substitutional incorporation of Ga atoms in the Zn sites based on a decrease in lattice spacing. The p-n diode structure with Ga-doped ZnO nanorods, as a n-type, displayed a distinct white light luminescence from the side-view of the device, showing weak ultraviolet and various deep-level emissions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.120-121
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• 2006

To investigate the ZnO thin films which are interested in the next generation of short wavelength LEDs and Lasers, the ZnO thin films were deposited by RF magnetron sputtering system. Al sputtering process of ZnO thin films substrate temperature, work pressure respectively is $100^{\circ}C$ and 15 mTorr, and the purity of target is ZnO 5N. The ZnO thin films were in-situ annealed at $600^{\circ}C$, $800^{\circ}C$ in $O_2$ atmosphere. Phosphorus (P) and arsenic (As) were diffused into ZnO thin films sputtered by RF magnetron sputtering system in ampoule tube which was below $5{\times}10^{-7}$ Torr. The dopant sources of phosphorus and arsenic were $Zn_3P_2$ and $ZnAS_2$. Those diffusion was perform at $650^{\circ}C$ during 3hr. We confirmed that p-type properties of ZnO thin films were concerned with dopant sources rather than diffusion temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.442-443
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• 2007

Al-N co-doped ZnO films were fabricated on n-Si (100) and homo-buffer layers in the mixture of oxygen and nitrogen at $450^{\circ}C$ by magnetron sputtering. Target was ZnO ceramic mixed with $2wt%Al_2O_3$. XRD spectra show that as-grown and $600^{\circ}C$ annealed films are prolonged along crystal c-axis. However they are not prolonged in (001) plane vertical to c-axix. The films annealed at $800^{\circ}C$ are not prolonged in any directions. Codoping makes ZnO films unidirectional variation. XPS show that Al content hardly varies and N escapes with increasing annealing temperature from $600^{\circ}C\;to\;800^{\circ}C$. The electric properties of as-grown films were tested by Hall Effect with Van der Pauw configuration show some of them to be p-type conduction.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.28.1-28.1
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• 2009

The superior properties of ZnO such as high exciton binding energy, high thermal and chemical stability, low growth temperature and possibility of wet etching process in ZnO have great interest for applications ranging from optoelectronics to chemical sensor. Particularly, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. Currently, low-dimensional ZnO is synthesized by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), thermal evaporation, and sol.gel growth. Recently, our group has been reported about achievement the growth of Ga-doped ZnO nanorods using ZnO seed layer on p-type Si substrate by RF magnetron sputtering system at high rf power and high growth temperature. However, the crystallinity of nanorods deteriorates due to lattice mismatch between nanorods and Si substrate. Also, in the growth of oxide using sputtering, the oxygen flow ratio relative to argon gas flow is an important growth parameter and significantly affects the structural properties. In this study, Phosphorus (P) doped ZnO nanorods were grown on c-sapphire substrates without seed layer by radio frequency magnetron sputtering with various argon/oxygen gas ratios. The layer change films into nanorods with decreasing oxygen partial pressure. The diameter and length of vertically well-aligned on the c-sapphire substrate are in the range of 51-103 nm and about 725 nm, respectively. The photoluminescence spectra of the nanorods are dominated by intense near band-edge emission with weak deep-level emission.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.354-354
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• 2012

In this study, we report the vertically aligned ZnO nanowires by using different type of Ga-doped ZnO (GZO) thin films as seed layers to investigate how the underlying GZO film micro structure affects the distribution of ZnO nanowires. Arrays of highly ordered ZnO nanowires have been synthesized on GZO thin film seed layer prepared on p-Si substrates ($7-13{\Omega}cm$) with utilize of a pulsed laser deposition (PLD). With the vapor-liquid-solid (VLS) growth process, the ZnO nanowire synthesis carries out no metal catalyst and is cost-effective; furthermore, The GZO seed layer facilitates the uniform growth of well-aligned ZnO nanowires. The influence of the growth temperature and various thickness of GZO seed layer have been analyzed. Crystallinity of grown seed layer was studied by X-Ray diffraction (XRD); diameter and morphology of ZnO nanowires on seed layer were investigated by field emission scanning electron microscopy (FE-SEM). Our results suggest that the GZO seed layer with high c-axis orientation, good crystallinity, and less lattice mismatch is key parameters to optimize the growth of well-aligned ZnO nanowire arrays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.177-177
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• 2007

ZnO는 3.36eV의 넓은 밴드캡을 가지는 II-IV족 반도체로써 태양전지, LED와 같은 광학적 소자로 이용이 기대가 되는 물질이다. 더욱이, 상온에서의 60meV에 해당하는 큰 엑시톤 에너지와 밴드캡 에지니어링이 가능하다는 장점 때문에 광학적 소자로 널리 이용되고 있는 GaN을 대체할 수 있는 물질로 주목을 받고 있다. 하지만, p-type ZnO는 형성이 어렵고 낮은 이동도와 케리어 농도의 특성을 보이고, 대기 중에 장시간 노출할 경우 n-type ZnO의 특성으로 돌아가는 불안정성을 보이고 있다. 최근에 몇몇의 연구자들에 의해 V족의 원소인 P(phosphorous), N(nitrogen), As(arsenic))를 도핑하여 p-type ZnO의 형성에 대한 논문이 발표되고 있다. 또한, V족 원소 중에 P는 p-type ZnO 형성에 효과적인 도핑 물질로 보고되 고 있다. 본 연구는 마그네트론 스퍼터링을 이용하여 다양한 온도에서 성장된 P도핑 ZnO 박막의 특성에 대해 연구하였다. P도핑된 ZnO 박막은 사파이어 기판에 buffer층을 사용한 Insulator 특성의 ZnO박막위에 400, 500, 600, $700^{\circ}C$에서 성장되 었다. 박막의 특성 분석에는 325nm의 파장을 가지는 He-Cd의 레이져 광원을 사용하여 10K의 저온 PL과 0.5T의 자기장을 사용한 van der Pauw configuration에 의한 Hall effect측정, 그리고 결정성 분석에는 XRD와 TEM을 이용하였다. 상온 Hall-effect 측정 결과, $400{\sim}600^{\circ}C$ 에서 성장된 박막은 n-type의 특성을 보였고, $700^{\circ}C$에서 성장된 Phosphorous 도핑 ZnO박막은 $1.19{\times}10^{17}$의 캐리어 농도를 가지는 p-type의 특성을 보였다. 그리고 XRD분석과 TEM분석을 통하여 박막의 성장온도가 증가 할수록 P도핑된 ZnO박막의 결정성이 향상되는 것을 알 수 있었다. 또한 10K의 저온 PL분석을 통해 p도핑에 의한 액셉터에 관련된 피크들을 관찰할 수 있었다.

• Solar Energy
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• v.17 no.3
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• pp.51-57
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• 1997

Cu-doped ZnTe thin films have been grown by hot-wall evaporation. The electrical conductivity of the intrinsic ZnTe film was of p-type and as low as $10^{-6}({\Omega}{\cdot}cm)^{-1}$. As the doped Cu concentration was increased, the electrical conductivity was increased. up to $10^2({\Omega}{\cdot}cm)^{-1}$, but the mobility was decreased a little. The heavily doped sample shows the metal-like electrical resistivity.