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준원자층 적층 방법으로 형성된 2형 양자점의 광 발광 특성 연구
김종수,조현준,소모근,김종수,김영호,이상준,이승현,Christiana B. Honsberg,김희대 한국물리학회 2019 새물리 Vol.69 No.8
We have studied the optical properties of InAs/GaAsSb submonolayer quantum dots (SML-QDs) through excitation intensity (Iex) and temperature dependent photoluminescence (PL) experiments. The SML-QDs with type-I (T-1) and type-II (T-2) band structures were grown using a GaAsSb spacer with a Sb composition of 0% and 15.8%. At 13 K, the PL signals from the T-1 and the T-2 samples were observed at 1.42 eV and 1.37 eV, respectively, when the Iex was 8.7 mW/cm2. The PL signal of the T-1 sample is due to the recombination of electrons and holes in the InAs SML-QDs. The PL signal of the T-2 sample is due to the recombination of electrons (in the GaAs electron band) and holes (in the GaAsSb spacer hole band) by type-II band alignment formed between GaAs and GaAsSb. The full widths at half maxima (FWHMs) of the T-1 and the T-2 samples were 7.09 meV and 24.6 meV, respectively, because the T-2 sample has a lower uniformity than the T-1 sample. As the excitation intensity was increased, the PL signals of the T-1 and the T-2 samples shifted to lower energy because of the quantum-confined Stark effect. As a result of these temperature-dependent PL experiments, the activation energy of the T-1 sample was found to be 30 meV. InAs/GaAsSb submonolayer 양자점(SML-QD)의 광학적인 특성을 여기광 세기(Iex)와 온도에 따른광발광 (Photoluminescence; PL) 실험을 통하여 연구하였다. 본 연구에 사용된 시료는 간격자인 GaAsSb 층의 Sb조성을 0%와 15.8%로 조절하여 Type-I (T-1) 과 Type-II (T-2) 밴드 구조의 SML-QD를 성장하였다. 13 K에서 Iex 가 8.3 mW/cm2 일 때 T-1과 T-2 시료의 PL신호는 각각 1.419 eV와 1.368 eV 에서 관측되었다. T-1 시료에서 관측된 전이신호는 InAs SML-QD의 전자와 정공간의 재결합에 의한것이다. T-2시료에서 관측된 PL신호는 GaAs와 GaAsSb 사이에 형성된 type-II 밴드 정렬에 의하여GaAs 전도대의 전자와 GaAsSb 간격자의 가전자대의 정공간의 재결합에 의한 것이다. 두 신호의 반값온폭 (Full-width at half maximum; FWHM)은 각각 7.09 meV와 24.6 meV 이었으며, 이는 T-2시료가T-1시료보다 균일성이 낮기 때문으로 사료된다. 여기광의 세기가 증가할수록 T-1와 T-2시료의 PL신호는낮은 에너지 쪽으로 이동하였는데, 이는 구속된 운반자에 의한 양자 구속 스타크 효과(quantum-confined Stark effect) 에 의한 것으로 사료된다. 온도 의존성 PL 실험의 결과, T-1 시료의 SML-QD의 활성화에너지는 30 meV이었다.
Hardware Implementation of GaN-HEMT Based ZVS DC–DC Converter Considering PCB Layout
김종수,김현빈,이병국,김종수 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.1
The gallium nitride high electron mobility transistors (GaN HEMT) are among the most promising power semiconductor devices. However, these transistors have a small gate voltage margin compared with conventional power devices. In this paper, the gate voltage of GaN HEMTs is mathematically analyzed when it is applied to a zero voltage switching (ZVS) phase-shift full bridge (PSFB) DC–DC converter. The analysis accounts for nonlinear capacitance characteristics under the ZVS switching condition, and a critical parasitic inductance are derived to restrict the gate voltage to a safety operation area. The optimal layout for bridge topologies and gate drivers is proposed, to satisfy the derived parasitic inductance limitation. A 500-W-power laboratory phase-shift full-bridge DC–DC converter is implemented to verify the proposed layout.
김종수,최승도,선우재근,배동한 순천향의학연구소 2004 Journal of Soonchunhyang Medical Science Vol.10 No.2
Osteogenesis Imperfecta(Ol) is a heritable disorder of which the defects make bones brittle, and is usually associated with blue sclerae, hearing loss, abnormalities of dentition, or a combination of these features. One of these, the perinatal form on OI TypeⅡ is rare disorder characterized by poorly ossified calvaria, beaded rib, and short, bowed limbs. We recently experienced a case of OI Type Ⅱ diagnosed in utero by ultrasonogram and confirmed by postnatal radiograph and autopsy. So, we report the case with a brief review of the literature.
김종수,조강래,Kim, J.S.,Cho, K.R. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.2
The effects of duct inlet conditions on fan characteristics and upper wind velocity fields were investigated for two kinds of impellers. As the duct inlet condition, the relative positions between duct inlet and fan impeller and the size of baffle plate mounted on a duct inlet were selected. The 3-dimensional velocity components in flow fields were measured by a 5-holes pitot tube. From the results of measurements, it was found that the size of baffle plate scarecely effect on upper wind flow fields and characteristics of fan. It was also confirmed that the upper wind velocity distributions can be estimated by the potential flow field with large baffle plate at duct inlet.
김종수,김성주,전홍태,최우경 대한전자공학회 2004 電子工學會論文誌-CI (Computer and Information) Vol.41 No.06
Most vehicles having automatic transmission system use fixed standard shift map to provide automatic transmission for driver. In this case, driver who operates vehicle may be complaint with the fixed transmission pattern being different from the driver's intention. In this paper, therefore, to infer the driver's intention module for learning the driver's intention with related input variables using soft computing method is proposed. After inference, the standard shift map will be shifted according to a certain parameter decided from the proposed module for providing proper shift pattern. The efficiency of the proposed module is evaluated by the data acquired from real time driving. 결정된 변속선도에 의한 자동변속 패턴은 운전자에게 편리한 변속을 제공한다. 하지만, 운전자의 운전 성향이 개인마다 다양함으로 고정된 변속선도를 여러 운전자에게 동일하게 제공하는 것은 불만의 요소로 인식되고 있다. 이에, 본 논문에서는 운전자의 성향을 결정할 수 있는 입력을 이용한 학습 모듈을 설계하여 운전 성향을 판단하고자 한다. 판단된 운전 성향을 이용하여 변속선도를 조정함으로써 운전자의 의지에 부합되는 변속패턴을 제공하고자 한다. 실제 주행 시 얻은 데이터를 이용하여 제안된 모듈의 성능의 우수함을 보인다.