• Applied Science and Convergence Technology
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• 제26권4호
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• pp.79-85
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• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• 소성∙가공
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• 제28권1호
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• pp.43-48
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• 2019

Aluminum nitride (AlN) is used by the semiconductor industry, and is a compound that is required when manufacturing high thermal conductivity. The AlN films with c-axis orientation and thermal conductivity characteristic were deposited by using the Pulsed Laser Deposition (PLD). The AlN thin films were characterized by changing the deposition conditions. In particular, we have researched the AlN thin film deposited under optimal conditions for growth atmosphere. The epitaxial AlN films were grown on sapphire ($c-Al_2O_3$) single crystals by PLD with AlN target. The AlN films were deposited at a fixed temperature of $650^{\circ}C$, while conditions of nitrogen ($N_2$) pressure were varied between 0.1 mTorr and 10 mTorr. The quality of the AlN films was found to depend strongly on the $N_2$ partial pressure that was exerted during deposition. The X-ray diffraction studies revealed that the integrated intensity of the AlN (002) peak increases as a function the corresponding Full width at half maximum (FWHM) values decreases with lowering of the nitrogen partial pressure. We found that highly c-axis orientated AlN films can be deposited at a substrate temperature of $650^{\circ}C$ and a base pressure of $2{\times}10^{-7}Torr$ in the $N_2$ partial pressure of 0.1 mTorr. Also, it is noted that as the $N_2$ partial pressure decreased, the thermal conductivity increased.

• 열처리공학회지
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• 제36권5호
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• pp.298-302
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• 2023

Transparent and conducting tungsten (W) doped indium oxide (IWO) thin films were deposited on the glass substrate by using RF magnetron sputtering and then electron irradiation was conducted to investigate the effect of electron irradiation on the optical and electrical properties of the films. The electron irradiated films showed three x-ray diffraction peaks of the In₂O₃ (222), (431) and (046) planes and the full width at half maximum values are decreased as increased electron irradiation energy. In the atomic force microscope analysis, the surface roughness of as deposited films was 1.70 nm, while the films electron irradiated at 700 eV, show a lower roughness of 1.28 nm. In this study, the figure of merit (FOM) of as deposited films is 2.07 × 10^-3 Ω^-1, while the films electron irradiated at 700 eV show the higher FOM value of 5.53 × 10^-3 Ω^-1. Thus, it is concluded that the post-deposition electron beam irradiation is the one of effective methods to enhance optical and electrical performance of IWO thin films.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.83-83
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• 2003

The stochiometric mix of evaporating materials for the CuInSe$_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CuInSe$_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were 62$0^{\circ}C$ and 41$0^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CuInSe$_2$ single crystal thin films measured from Hall effect by van der Pauw method are 9.62$\times$10$^{16}$ cm$^{-3}$ , 296 $\textrm{cm}^2$/V.s at 293 K, respectively From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the CuInSe$_2$ single crystal thin film, we have found that the values of spin orbit splitting ΔSo and the crystal field splitting ΔCr were 6.1 meV and 175.2 meV at 10 K, respectively. From the photoluminescence measurement on CuInSe$_2$ single crystal thin film, we observed free excition (Ex) existing only high quality crystal and neutral bound exiciton (D$^{\circ}$,X) having very strong peak intensity. Then, the full-width-at -half-maximum(FWHM) and binding energy of neutral donor bound excition were 7 meV and 5.9 meV, respectivity. By Haynes rule, an activation energy of impurity was 59 meV.

• 한국인터넷방송통신학회논문지
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• 제10권1호
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• pp.7-13
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• 2010

질소 분위기하에서 분자선 에피탁시 장치로 성장한 GaN 에피층을 고온 열처리 하였다. 시료는 적절한 조건하에서 급속 열처리 후 구조적인 특성의 향상을 나타내었다. 시료의 결정성의 향상은 에피층의 격자 관련 요소들의 흐트러짐의 감소에 기인한다. 에피층의 열처리는 950도의 급속 열처리로를 이용하여 수행하였다. 고온 급속 열처리가 GaN 에피층의 구조적인 특성들에 미치는 효과는 x선 회절을 통하여 연구하였다. x선 회절 스펙트럼에 있어서 Bragg 피크는 열처리 시간이 증가할수록 각도가 큰 쪽으로 이동하였다. 또한 피크의 FWHM은 열처리 시간이 증가함에 따라 약간의 증가 후 감소하였으며 이후 다시 증가하였다. 이와 같은 결과는 급속 고온 열처리된 GaN 에피층에서 격자 상수에 영향을 미치는 인자들이 에피층의 품질을 좋게 하는 방향으로 일률적으로 변화하는 것이 아니라 에피 품질을 나쁘게 하는 방향으로도 변화한다는 것을 의미한다. 적절한 조건 하에서의 급속 열처리는 에피층의 격자 상수에 관여하는 인자들의 흐트러짐을 감소시켜 에피 결정의 질을 향상시킨다.

• 한국분말재료학회지
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• 제23권5호
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• pp.348-352
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• 2016

Quantum dots (QDs) are capable of controlling the typical emission and absorption wavelengths because of the bandgap widening effect of nanometer-sized particles. These phosphor particles have been used in optical devices, photovoltaic devices, advanced display devices, and several biomedical complexes. In this study, we synthesize ZnSe QDs with controlled surface defects by a heating-up method. The optical properties of the synthesized particles are analyzed using UV-visible and photoluminescence (PL) measurements. Calculations indicate nearly monodisperse particles with a size of about 5.1 nm at $260^{\circ}C$ (full width at half maximum = 27.7 nm). Furthermore, the study results confirm that successful doping is achieved by adding $Eu^{3+}$ preparing the growth phase of the ZnSe:Eu QDs when heating-up method. Further, we investigate the correlation between the surface defects and the luminescent properties of the QDs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.125-126
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• 2006

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films. $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}cm^{-3}$. $345cm^2/V{\cdot}s$ at 293 K, respectively. From the photoluminescence measurement on $CdGa_2Se_4$ single crystal thin film, we observed free excition ($E_x$) existing only high quality crystal and neutral bound exiciton ($D^{\circ},X$) having very strong peak intensity. Then. the full-width-at -half-maximum(FWHM) and binding energy of neutral donor bound excition were 8 meV and 13.7 meV, respectivity. By Haynes rule. an activation energy of impurity was 137 meV.

• 한국결정성장학회지
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• 제26권2호
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• pp.58-61
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• 2016

Basic 암모노써멀 방법을 사용하여 벌크 GaN 단결정을 성장시켰다. 종자 결정은 Hydride vapor phase epitaxy법으로 성장한 c면의 GaN 템플릿을 사용하고 광화제는 sodium metal, amide, azide를 사용하였다. 결정 성장 온도는 $500{\sim}600^{\circ}C$, 성장 압력은 2~3 kabr에서 실시하였다. c 축의 결정 성장 속도는 운용 압력이 증가함에 따라 선형적으로 증가하였다. Cathodoluminescence로 측정한 평균 전위 밀도는 $1{\times}10^5/cm^2$였다. Double Crystals X-ray Diffraction로 측정한 (002)면의 반치폭은 Ga 면에 대해서는 약 270 arcsec, N 면에 대해서는 약 80 arcsec이었다.

• 한국의학물리학회지:의학물리
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• 제18권1호
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• pp.13-19
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• 2007

본 연구에서는 유리선량계가 방사선 치료장비의 선량계로서의 적정성 여부를 확인하고자 감마나이프의 출력인자 및 X축 측방선량분포를 측정하였다. 출력인자는 가장 큰 콜리메이터인 18mm의 측정값을 기준으로 하여 14, 8 그리고 4mm에 대해 상대적으로 측정하였고 그 결과 각각 $0.980{\pm}0.013,\;0.949{\pm}0.013$ 그리고 $0.872{\pm}0.012$로 나타났다. 이는 제작회사에서 제공하고 있는 표준데이터와 모든 콜리메이터에서 1.0% 이내에서 잘 일치하는 결과이다. 또한 유리선량계로 측정한 4mm 콜리메이터의 x축 측방선량분포의 반치폭은 5.9mm였다.

• 한국세라믹학회지
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• 제39권2호
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• pp.210-215
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• 2002

본 연구에서는 $CO_2$ 흡수단이 있는 4.3${\mu}m$ 파장대역의 광학 필터를 전자빔 증발 장치를 이용하여 Ge와 $SiO_2$ 박막을 다층으로 설계, 제작하였다. 제작된 Ge/$SiO_2$ 다층박막 필터는 기준파장에 대하여 반가폭(FWHM) 204nm, 투과율 58.2%, 금지대역에 대하여 5% 이하의 차단특성을 나타내는 협대역 투과필터 (narrow band-pass filter: BPF)특성을 나타내었다. 광학적 대역투과필터를 사용하여, FT-IR내에 감지실을 설치하여 단식 필터(KBr+BPF)와 복식필터(BPF+BPF)의 $CO_2$ 농도별 감도특성을 비교측정 하였다. 측정시 $CO_2$의 농도는 500ppm을 단위로 500∼5000ppm의 범위까지 관찰하였는데, 복식 필터는 단식 필터에 비해 투과율이 낮았지만, 우수한 감도 특성을 보였다.