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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.
신수혈의 침자극과 황기약침이 실험용 생쥐의 면역활성물질인 cytokine의 IL-6 발현에 미치는 영향
김종수,신상습,김철호,박선동,박원환,Kim Jong-Soo,Sin Sang-Sup,Kim Cheul-Ho,Park Sun-Dong,Park Won-Hwan 대한침구의학회 1998 대한침구의학회지 Vol.15 No.2
Acupuncture and Radix Astragali aqua-acupuncture stimuli have long been used to cure human diseases. However, it still remains to be unkown on its action mechanism, physiolosical and biochemical aspects. Thus, many attempts were made to show the scientific background covering the above mentioned mechanisms. Most recent studies show that these tests improve blood circulatory system and increase leucocyte counts. In this study, we have applied the acupuncture stimuli to mouse Sinsu(BL-23), which is a stimulative point of oriental medicine, to see if cytokine such as IL-6 can be detected. Mice were treated with lipopolysaccharide(LPS) for inflammation induction, and then reverse transcriptase-polymerase chain reaction (RT-PCR) using each primer set was performed to trace the amounts of mRNA. The results are summarized as follows ; 1. IL-6 was not temporarily expressed in normal mice 15 min after the acupuncture was pulled out. But, it started to show a feeble expression at 30 min after the removal of acupuncture and it started to reduce at 1h. after the acupuncture was pulled out 2. IL-6 was specifically expressed in LPS-treated mouse 30 min after the acupuncture was pulled out. The transcriptional expressions of LPS-treated mice were more effective than those of normal mice at 30 min after the removal of acupuncture 3. IL-6 was not temporarily expressed in normal mice 15 min after Radix Astragali aqua-acupuncture. But it expressed most highly at 30 min, and the transcriptional expressions of IL-6 was continued to 3 h. 4. IL-6 was not expressed in all the time after Radix Astragali aqua-acupuncture in LPS-treated mice. Therefore, a follow-up of cytokine IL-6 can be used not only a basis of the effect of acupuncture and Radix Astragali aqua-acupuncture but a diagnosis giude through the immunological action of thats. And, it is suggested that cytokine's expression by Acupuncture and Radix Astragali aqua-acupuncture stimulation should be continuously elucidated.