• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.217-223
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• 2010

We grew multi-stacked InAs/$In_{0.1}Ga_{0.9}As$ DWELL (dot-in-a-well) structure by metal organic chemical vapor deposition and investigated optical properties by photoluminescence and I-V characteristics by dark current measurement. When stacking InAs quantum dots (QDs) with same growth parameter, the size and density of QDs were changed, resulting in the bimodal emission peak. By decreasing the flow rate of TMIn, we achieved the uniform multi-stacked QD structure which had the single emission peak and high PL intensity. As the growth temperature of n-type GaAs top contact layer (TCL) is above $600^{\circ}C$, the PL intensity severely decreased and dark current level increased. At bias of 0.5 V, the activation energy for temperature dependence of dark current decreased from 106 meV to 48 meV with increasing the growth temperature of n-type GaAs TCL from 580 to $650^{\circ}C$. This suggest that the thermal escape of bounded electrons and non-radiative transition become dominant due to the thermal inter-diffusion at the interface between InAs QDs and $In_{0.1}Ga_{0.9}As$ well layer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.149-153
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• 2021

ε-Ga₂O₃ thin films were grown on 4H-SiC substrates by metal organic chemical vapor deposition (MOCVD) and crystalline quality were evaluated depend on growth conditions. It was found that the best conditions of the ε-Ga₂O₃ were grown at a growth temperature of 665℃ and an oxygen flow rate of 200 sccm. Two-dimensional growth was completed after the merge of hexagonal nuclei, and the arrangement direction of hexagonal nuclei was closely related to the crystal direction of the substrate. However, it was confirmed that crystal structure of the ε-Ga₂O₃ had an orthorhombic rather than hexagonal. Crystal phase transformation was performed by thermal treatment. And a β-Ga₂O₃ thin film was grown directly on 4H-SiC for the comparison to the phase transformed β-Ga₂O₃ thin film. The phase transformed β-Ga₂O₃ film showed better crystal quality than directly grown one.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1281-1287
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• 2018

In this study, $Al_xGa_{1-x}N$ films were grown on (0001) sapphire substrates by using metal-organic chemical vapor deposition (MOCVD). The crystallinity of the grown films was examined with X-ray diffraction (XRD) patterns. The surfaces and the chemical properties of the $Al_xGa_{1-x}N$ films were investigated using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The optical properties of the $Al_xGa_{1-x}N$ film were studied in a wide photon energy range between 2.0 ~ 8.7 eV by using spectroscopic ellipsometry (SE) at room temperature. The data obtained by using SE were analyzed to find the critical points of the pseudodielectric function spectra, $<{\varepsilon}(E)>=<{\varepsilon}_1(E)>+i<{\varepsilon}_2(E)>$. In addition, the second derivative spectra, $d^2<{\varepsilon}(E)>/dE^2$, of the pseudodielectric function for the $Al_xGa_{1-x}N$ films were numerically calculated to determine the critical points (CPs), such as the $E_0$, $E_1$, and $E_2$ structure. For the four samples (x = 0.18, 0.21, 0.25, 0.29) between a composition of x = 0.18 and x = 0.29, changes in the critical points (blue-shifts) with increasing Al composition at 300 K for the $Al_xGa_{1-x}N$ film were observed via ellipsometric measurements for the first time.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.29.2-29.2
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• 2010

최근 박막형 LED 및 박막형 태양전지등의 기존 마이크로 소자들의 효율향상을 위한 개선으로 나노구조를 이용한 나노소자 제작이 관심을 받고 있다. 이는 가능성으로만 여겨져왔던 나노기술이 기존 박막형 소자에서 포화된 효율상향 접근방식의 한계에 따른 것으로 생각되며, 나아가 나노기술로 제작된 나노소자가 우리 생활을 채우게 될 날이 얼마남지 않은 것을 의미한다. 특히, 디스플레이 소자에서의 나노기술은 더욱 더 중요시 되고 있다. 그로 인해 투명성과 우수한 광전기적 특성을 지닌 산화물 반도체와 그 나노구조 대한 관심이 날로 높아지고 있으며, 그 가운데 산화아연계(ZnO, MgZnO등) 나노구조를 이용한 나노소자 제작이 많이 연구되고 있다. 산화아연은 c축으로 우선 배향성을 가지는 우르짜이트 구조로써, 나노선 성장이 다른 산화물에 비해 용이하고 그 물리적, 화학적 특성이 안정 우수하다. 이러한 산화아연 나노선 제작법 가운데, 유기금속화학기상증착법은 다른 성장법에 비해 결정학적 광학적 특성이 우수하고 성장속도가 빨라 고품질 나노선 성장에 용이한 장비로 각광받고 있다. 하지만 bottom-up 공정을 기반으로 한 나노소자제작에서 몇 가지 문제점을 가지고 있다. 1) 수직형 대면적 성장, 2) 나노선 밀도 조절의 어려움, 3) 기판과의 계면층에 자발적으로 생성되는 계면층의 제거, 4) 고온성장시 precursor의 증발 문제 등이 그것이다. 이러한 문제점을 해결하기 위해 산화아연 나노구조 성장 시, 마그네슘(Mg)을 도입하여, 각 원소의 조성 차이에 따라 기판 표면에 30nm 두께 미만의 상분리층(단결정+비정질층)을 자발적으로 형성시켰다. 성장이 진행됨에 따라, 아연이 rich한 단결정 층에서는 나노선이 선택적으로 성장하게 하였고, 마그네슘이 rich한 비정질 층에서는 성장이 이루어지지 않게 하였다. 따라서 산화아연이 증발되는 온도영역에서 10nm 이하 직경을 가지는 나노선을 자발적으로 계면층 없이 수직 성장하였다. 또한, 표면의 단결정, 비정질의 사이즈를 Mg 유량으로 적절히 조절한 결과, 산화아연계 나노월 구조성장이 가능하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.125-131
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• 2023

Ga₂O₃ thin films were deposited on Ti substrates using metal organic chemical vapor deposition (MOCVD) at temperatures ranging from 350 to 500℃. Lower deposition temperatures were chosen to minimize thermal deformation of the Ti substrate and its impact on the Ga₂O₃ film. Film surfaces tended to become rough at temperatures below 500℃ due to three-dimensional growth, but the film formed at 500℃ had the most uniform surface. All deposited films were amorphous in structure. Vertical Schottky diodes were fabricated and I-V and C-V measurements were performed. I-V measurements showed higher operating voltages compared to a typical SBD for films grown at different temperatures. The sample grown at 500℃, which had the most uniform surface, exhibited the lowest operating voltage. Higher growth temperatures resulted in higher capacitance values according to C-V measurements.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1128-1132
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• 2002

$ReMnO_3$(Re:Y, Ho, Er) thin films were prepared by MOCVD method available to non-volatile memory device with MFS-FET structure. $ReMnO_3$ thin films were deposited on the Si(100) substrate at 700${\circ}C$ for 2h. When the films were post-annealed at 900${\circ}C$ for 1h in air, the single phase of hexagonal $ReMnO_3$ thin films were detected. Ferroelectric properties of $ReMnO_3$ thin films were dependent on the degree of c-axis orientation in the single phase of hexagonal structure and remnant polarization (Pr) of $YMnO_3$ thin films with high degree of c-axis orientation was 105 nC/$cm^2$. Leakage current density was dependent on the grain size of microstructure and that of $YMnO_3$ thin films with grain size of 100∼150 nm was $10^{-8}$ A/$cm^2$ at applied voltage of 0.5 V.

• Korean Journal of Materials Research
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• v.10 no.4
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• pp.282-289
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• 2000

$PbTiO_3$ films were fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition(ECR-PECVD). Deposition characteristics of $PbTiO_3$films on $RuO_2$ and Pt substrates were investigated with varying the flow rate of metalorganic source and substrate temperature. The residence time of Pb-oxide molecules in much longer on $RuO_2$ than on Pt substrate, while the perovskite nucleation is more difficult on $RuO_2$ than on Pt substrate. Therefore, the process conditions to obtain the single perovskite $PbTiO_3$ phase are more restricted on $RuO_2$ than on Pt substrates. An introduction of Ti-oxide seed layer increases perovskite nucleation density and thus enlarges the process window to obtain the single perovkite phase. The introduction of Ti-oxide seed layer make the PZT film that Ti-components of $PbTiO_3$ are partially substituted with Zr atoms have single perovskite phase for the wide range of Zr/(Zr+Ti) concentration ratios.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.22-22
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• 2009

최근 산화물 반도체와 나노소자 대한 관심이 날로 높아지고 있는 가운데 산화아연(ZnO) 나노구조를 이용한 나노소자 제작이 많이 연구되고 있다. 산화아연은 c축으로 우선 배향성을 가지는 우르짜이트 구조로써, 나노선 성장이 다른 산화물에 비해 용이하고 그 물리적, 화학적 특성이 안정 무수하다. 이러한 산화아연 나노선 제작법 가운데, 유기금속화학기상증착법은 다른 성장법에 비해 결정학적 광학적 특성이 우수하고 성장속도가 빨라 고품질 나노선 성장에 용이한 장비로 각광받고 있다. 하지만 bottom-up 공정을 기반으로 한 나노소자제작에서 몇 가지 문제점을 가지고 있다. 1) 수직형 대면적 성장, 2) 나노선 밀도 조절의 어려움, 3) 기판과의 계면층에 자발적으로 생성되는 계면층의 제거, 4) 고온성장시 precursor의 증발 문제 등이 그것이다. 본인은 이러한 문제점을 해결하기 위해 산화아연 나노구조 성장 시, 마그네슘(Mg)을 도입하여, 각 원소의 함량 분포 정도에 따라 기판 표면에 30nm 두께 미만의 상분리층(단결정+비정질층)을 자발적으로 형성시켰다. 성장이 진행됨에 따라, 아연이 rich한 단결정 층에서는 나노선이 선택적으로 성장하게 하였고, 마그네슘이 rich한 비정질 층에서는 성장이 이루어지지 않게 하였다. 따라서 산화아연이 증발되는 온도영역에서 10nm 이하 직경을 가지는 나노선을 자발적으로 계면층 없이 수직 성장하였다. 또한, 표면의 단결정, 비정질의 사이즈를 Mg 함량으로 적절히 조절한 결과, 산화아연계 나노월 구조성장이 가능하였다.

• Journal of the Korean Vacuum Society
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• v.5 no.3
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• pp.206-212
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• 1996

$In_{1-x}Ga_xAs$ epitaxial layers were grown at 76 Torr by low pressure metalorganic chemical vapor deposition (LP-MOCVD). Growth rate did not change much with growth temperature. Surface morphology of $In_{1-x}Ga_xAs$ epitaxial layer was affected by lattice mismatch, growth temperature and $AsH_3/(TMIn+TMGa)$ ratio. A high quality epilayer showed a full width at half maximum of 2.8 meV by photoluminescence measurement at 5K. The composition of the $In_{1-x}Ga_xAs$ was determined by the relative gas phase diffusion of TMIn and TMGa. Lattice mismatch and growth temperature were the most important variables that determine the electrical properties of $In_{1-x}Ga_xAs$ epitaxial layers. At optimized growth condition, it was possible to obtain a high quality $In_{1-x}Ga_xAs$ epilayers with a electron concentration as low as $8{\times}10^{14}/cm^3$ and an electron mobility as high as 11,000$\textrm{cm}^2$/Vsec at room temperature.

• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1216-1221
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• 1999

GaN films were deposited on sapphire [$Al_2O_3(0001)$] substrates at relatively low temperature by MOCVD using N-atom source based on a Dielectric Barrier Discharged method. Ammonia gas($NH_3$is commonly used as an N-source to grow GaN films in conventional MOCVD process, and heating to high temperature is required to provide sufficient dissociation of $NH_3$. We used a dielectric barrier discharge method instead of $NH_3$ to grow GaN film relatively low temperature. DBD is a type of discharge, which have at least one dielectric material as a barrier between electrode. DBD is a type of controlled microarc that can be operated at relatively high gas pressure. Crystallinity and surface morphology depend on growth temperature and buffer layer growth. With the DBD-MOCVD method, wurtzite GaN which is dominated by the (0001) reflection was successfully grown on sapphire substrate even at $700^{\circ}C$.