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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.
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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.
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男學生의 넓이뛰기 鍊習 結果에 關한 分析 : 도움닫기를 中心으로 Centering on ruuning retained intervals and jumping
金鍾洙 圓光大學校 1978 論文集 Vol.12 No.-
Ⅰ. Running retained intervals, jumping and problem of its record : the purpose of this thesis is to survey the relation between running retained intervals and problem of its record. Accorting to the statistics of the distance in the running retained intervals and jumping, the difference of record in the running retained intervals and jumping resulted in p>0.005 in mutual C.R.testing, which showed a meaninful disparity. It has been indicated that the adequate distance for junior high schoolboys in the running maintained intervals and jumping is between 25m and 35m 2. The investigation of personnel distribution who hold the highest record by the distance resulted in about 25% at the 35m, distance in the running retained intervals, about 16% at 30m, about 26% at 25m, about 12% at 20m, and the rest is between 40m and 15m distances. As the distribution is scattered, the distance in the running retained intervals and jumping must be decided in accordance with the physical condition of individuals and the amount of practice. Ⅱ. Retation between speed in the running retained intervals and its record: As a result of analysis of time required in the running retained intervals and jumping by the distance which resulted with the highest record, a man who increase the speed is capable of doing the running retaind intervals at a short distance. Time required in the running retained intervals and jumping when the highest record was estabrished was investigared by five units and the section and resulted in 1.3 times 0.5 averave hour required at 0 to 15m(15m intervals), 100m average speed at the section from 15m to 20m(5m intervals), 0.58 times between 20m and 25m or between 25m and 30m at the fastest speed, 10.6 times at the section of 30m and 35m, which speed slowed, 10.8 times of hour required from 35m to 40m, which is somewhat rate. survey was also made concentrating on the person who established the hightest record at 35m section, but similar state was maintained. Ⅲ. Distance problem of the running retained intervals and jumping between number of foot convey and span of step: The survey was made as to number of foot convey and spanof step by the distance of running retained intervals and jumping (15m to 40m) and obtained the result that the nearer the distnce was, the farther the number of foot farther, the number of foot convey reduced and span of step broadned when conpared with the distance. Ⅵ. Physical Condition and distance problem in the running retained intervals and jumping: According to the statistics obtained through the survey of height and weight by the distance of running retained intervals and jumping when the highest record was estableshed, a man who is short in height and righ weight established the highest record at a short distance(20m to 25m) and a man who is long in height and heavy weight established the highest record at a far distance(above 35m). The writer arrived the conclusion that, as height is long and weight is heavy, the distance for the running retained intervals and jumping should be farther.
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