열유체해석 모델의 병렬화

곽호상 대한기계학회 2002 기계저널 Vol.42 No.1

Al0.3Ga0.7N/GaN 및 Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN 이종접합 구조에서 운반자 구속 효과와 이차원 전자가스의 광학적 특성

곽호상,이규석,조현익,이정희,조용훈 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.4

금속 유기화학 증착기 (metal-organic chemical vapor deposition)를 이용하여 사파이어 기판 위에 Al0.3Ga0.7N/GaN 및 Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN 이종접합 구조들을 성장하고, 이들 시료의 전자와 정공들 간의 구속 효과를 조사하기 위하여 광학적, 구조적 특성을 비교하였다. 저온 (10 K) photoluminescence 실험으로부터 Al0.3Ga0.7N/GaN 단일 이종접합 구조의 경우 3.445 eV에서 단일의 이차원 전자가스 (two-dimensional electron gas; 2DEG) 관련된 발광을 관찰한 반면, Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN 다중 이종접합 구조의 경우 3.445 eV에서 뿐만 아니라, 3.42 eV에서 추가적인 2DEG 관련된 발광을 관찰 할 수 있었다. 이 두 개의 2DEG 관련 신호들의 근원을 조사하기 위하여 Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN 다중 이종접합구조에서의 에너지 밴드 구조를 이론적으로 계산하여 실험과 비교한 결과, 하나의 2DEG에 의한 서로 다른 버금띠로 부터가 아닌 다중 구조에 형성된 두 개의 2DEG로부터의 신호로 해석되었다. We have investigated optical and structural properties of Al0.3Ga0.7N/GaN and Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN heterostructures (HSs) grown by metal-organic chemical vapor deposition, by means of Hall measurement, high-resolution X-ray diffraction, and temperature- and excitation power-dependent photoluminescence (PL) spectroscopy. A strong GaN band edge emission and its longitudinal optical phonon replicas were observed for all the samples. At 10 K, a 2DEG-related PL peak located at ~ 3.445 eV was observed for Al0.3Ga0.7N/GaN HS, while two 2DEG peaks at ~ 3.42 and ~ 3.445 eV were observed for Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN HS due to the additional Al0.15Ga0.85N layers. Moreover, the emission intensity of the 2DEG peak was higher in Al0.3Ga0.7N/GaN/Al0.15Ga0.85N/GaN HS than in Al0.3Ga0.7N/GaN HS probably due to an effective confinement of the photo-excited holes by the additional Al0.15Ga0.85N layers. The 2DEG-related emission intensity decreased with increasing temperature and disappeared at temperatures above 150 K. To investigate the origin of the new 2DEG peaks, the energy-band structure for multiple AlGaN/GaN HSs were simulated and compared with the experimental data. As a result, the observed high- and low-energy peaks of 2DEG can be attributed to the spatially-separated 2DEG emissions formed at different AlGaN/GaN heterointerfaces.

Automated Wafer Separation from the Stacked Array of Solar Cell Silicon Wafers Using Continuous Water Jet

곽호상,김경진,김동주 한국반도체디스플레이기술학회 2010 반도체디스플레이기술학회지 Vol.9 No.2

In response to the industrial needs for automated handling of very thin solar cell wafers, this paper presents the design concept for the individual wafer separation from the stacked wafers by utilizing continuous water jet. The experimental apparatus for automated wafer separation was constructed and it includes the water jet system and the microprocessor controlled wafer stack advancing system. Through a series of tests, the performance of the proposed design is quantified into the success rate of single wafer separation and the rapidity of processing wafer stack. Also, the inclination angle of wafer equipped cartridge and the water jet flowrate are found to be important parameters to be considered for process optimization. The proposed design shows the concept for fast and efficient processing of wafer separation and can be implemented in the automated manufacturing of silicon based solar cell wafers.

도핑이 되지 않은 AlGaN/GaN 단일이종접합에 형성된이차원전자가스로 인한 발광 천이 특성

곽호상,조용훈,배성범,이규석,이재훈,이정희 한국물리학회 2006 새물리 Vol.53 No.5

The optical properties of an undoped Al$_{0.3}$Ga$_{0.7}$N/GaN single heterostructure grown by using metal-organic chemical vapor deposition were studied by means of reflection, transmission, photoluminescence (PL) and PL excitation spectroscopy. Additional two-dimensional electron-gas (2DEG)-related emissions appeared below the GaN band-edge emission energy. From the excitation-power dependent PL spectra, two separate emissions, at 361.1 nm (E$_A$ peak) and at 359.7 nm (E$_B$ peak), related to the 2DEG were observed with an energy separation of 15.3 meV. To investigate the origin of the new 2DEG peaks, we simulated the energy sub-band structure for the undoped Al$_{0.3}$Ga$_{0.7}$N/GaN single heterostructure and compared it with the experimental data. As a result, the observed E$_A$ and E$_B$ peaks can be attributed to transitions from the first excited sub-band (E$_1$) and the Fermi energy (E$_F$) at the AlGaN/GaN heterointerface, respectively. 금속유기화학기상증착법을 이용하여 성장된 도핑이 되지 않은 Al$_{0.3}$Ga$_{0.7}$N/GaN 단일 이종접합구조에서의 광학적 특성을 반사, 투과, photoluminescence (PL), PL excitation 분광 방법을 사용하여 조사하였다. 이차원 전자가스로 인한 새로운 신호는 GaN band-edge 발광 (emission) 에너지 보다 아래에서 관측되었다. 여기광 세기에 따른 PL 실험으로부터, 이차원 전자가스로 인한 두 개의 발광들이 361.1 nm (E$_A$ 신호)와 359.7 nm (E$_B$ 신호)에서 약 15.3 meV의 에너지 차이를 가지고 관측되었다. 이차원 전자가스 관련 신호들의 근원을 조사하기 위하여 Al$_{0.3}$Ga$_{0.7}$N/GaN 단일 이종접합구조의 에너지 구조와 파동함수를 이론적으로 계산하고 실험과 비교한 결과, 실험적으로 관측된 E$_A$와 E$_B$ 신호들의 근원이 AlGaN/GaN 이종접합계면에서의 first excited 버금띠 (E$_1$)과 페르미 준위 (E$_F$)로 인한 천이로 각각 해석되었다.

저온 성장 AlN 층이 삽입된 Al0.55Ga0.45N/AlN/GaN 이종접합 구조의 구조적 특성 및 이차원 전자가스의 광학적 특성

곽호상,이규승,김희진,윤의준,조용훈 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.1

We have investigated the characteristics of Al0.55Ga0.45N/GaN heterostructures with and without low-temperature (LT) AlN interlayer grown by metalorganic chemical vapor deposition. The structural and optical properties were systematically studied by Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), optical microscopy (OMS), scanning electron microscopy (SEM), and photoluminescence (PL). The Al content (x) of 55% and the structural properties of AlxGa1-xN/GaN heterostructures were investigated by using RBS and XRD, respectively. We carried out OMS and SEM experiments and obtained a decrease of the crack network in Al0.55Ga0.45N layer with LT-AlN interlayer. A two-dimensional electron gas (2DEG)-related PL peak located at ~ 3.437 eV was observed at 10 K for Al0.55Ga0.45N/GaN with LT-AlN interlayer. The 2DEG-related emission intensity gradually decreased with increasing temperature and disappeared at temperatures around 100 K. In addition, with increasing the excitation power above 3.0 mW, two 2DEG-related PL peaks were observed at ~ 3.411 and ~ 3.437 eV. The observed lower-energy and higher-energy side 2DEG peaks were attributed to the transitions from the sub-band level and the Fermi energy level of 2DEG at the AlGaN/LT-AlN/GaN heterointerface, respectively. 저온에서 성장된 AlN (LT-AlN)층이 삽입된 AlxGa1-xN/LT-AlN/GaN 이종접합 구조를 금속유기 화학기상 증착법 (metal-organic chemical vapor deposition)을 사용하여 사파이어 기판 위에 제작하였다. Rutherford backscattering spectroscopy 실험을 통하여 AlxGa1-xN층의 Al의 조성비 x가 55% 임을 확인하였고, X-선 역격자 공간 mapping을 통하여 층간 변형력을 조사하였다. LT-AlN층의 삽입 여하에 따른 Al0.55Ga0.45N 층의 깨짐 현상을 광학현미경과 주사전자현미경을 통하여 조사하였는데, LT-AlN 층이 삽입된 시료의 경우에 깨짐 현상이 현저히 줄어든 Al0.55Ga0.45N 층을 얻을 수 있었다. 뿐만 아니라 LT-AlN 층이 삽입된 Al0.55Ga0.45N/LT-AlN/GaN 이종접합 구조에 대하여 이차원 전자가스 (two-dimensional electron gas, 2DEG) 관련된 photoluminescence (PL) 신호를 관찰하였다. 이 시료에 대하여 온도 변화에 따른 PL 실험을 수행하여 100 K 근방까지 2DEG 관련된 PL 신호를 관찰하였다. 여기광 세기에 따른 PL 실험을 통하여 ~3.411 eV에서 나타난 2DEG PL 신호와 함께 ~3.437 eV에서도 PL 신호가 관측되었는데, 이는 AlGaN/LT-AlN/GaN 계면에 형성된 2DEG 버금띠와 Fermi 에너지 준위에서의 재결합 특성으로 각각 해석되었다.

A Pseudospectral Method for the Three-Dimensional Navier-Stokes Equations in Cylindrical Coordinates

곽호상,현재민,성형진 대한기계학회 1990 대한기계학회 춘추학술대회 Vol.- No.-

A model for allometric scaling of mammalian metabolism with ambient heat loss

곽호상,Hong G. Im,심은보 한국한의학연구원 2016 Integrative Medicine Research Vol.5 No.1

Background Allometric scaling, which represents the dependence of biological traits or processes on body size, is a long-standing subject in biological science. However, there has been no study to consider heat loss to the ambient and an insulation layer representing mammalian skin and fur for the derivation of the scaling law of metabolism. Methods A simple heat transfer model is proposed to analyze the allometry of mammalian metabolism. The present model extends existing studies by incorporating various external heat transfer parameters and additional insulation layers. The model equations were solved numerically and by an analytic heat balance approach. Results A general observation is that the present heat transfer model predicted the 2/3 surface scaling law, which is primarily attributed to the dependence of the surface area on the body mass. External heat transfer effects introduced deviations in the scaling law, mainly due to natural convection heat transfer, which becomes more prominent at smaller mass. These deviations resulted in a slight modification of the scaling exponent to a value < 2/3. Conclusion The finding that additional radiative heat loss and the consideration of an outer insulation fur layer attenuate these deviation effects and render the scaling law closer to 2/3 provides in silico evidence for a functional impact of heat transfer mode on the allometric scaling law in mammalian metabolism.

Double-diffusive Fluid Flows in a Rotating Chamber

곽호상,현재민 대한기계학회 1987 대한기계학회 춘추학술대회 Vol.- No.-

Fabrication of InP/InGaAs/InP distributed feedback grating structure and its effect on the formation of InAs/InAlGaAs quantum dot

곽호상,김진수,이진홍,홍성의,최병석,오대곤,조용훈 한국진공학회 2006 한국진공학회 학술발표회초록집 Vol.15 No.1

기상 방법으로 성장된 ZnO 나노선 구조에서 공간적으로 형성된 donor bound exciton 특성에 대한 cathodoluminescence 연구

곽호상,Le Si Dang,조용훈 한국진공학회 2009 한국진공학회 학술발표회초록집 Vol.37 No.-