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Lee, Kwanjae,Lee, Cheul-Ro,Chung, Tae-Hoon,Park, Jinyoung,Leem, Jae-Young,Jeong, Kwang-Un,Kim, Jin Soo Elsevier 2017 Journal of crystal growth Vol.464 No.-
<P><B>Abstract</B></P> <P>In this paper, the influence of a Si-doped graded superlattice (SiGSL) on the electrostatic discharge (ESD) characteristics of green InGaN/GaN light-emitting diodes (LEDs) is discussed. To investigate the effects of Si doping to the superlattice, green LEDs were also fabricated on undoped graded superlattice (unGSL). Furthermore, a conventional green InGaN/GaN LED without the superlattice (C-LED), emitting at a wavelength of 534nm, was also prepared as a reference. The current-voltage (I-V) curves for the C-LED and the unGSL-LED subjected to the ESD treatments at surge voltages from 2000 to 8000V showed a drastic increase in the leakage current. However, there was relatively small change in the I-V curves for the SiGSL-LED after the ESD treatments, even at the surge voltages of 6000 and 8000V. After the ESD treatment at a surge voltage of 8000V, the EL intensities for the C-LED, unGSL, and SiGSL, measured at a driving current of 120mA, were reduced by 55, 53, and 30%, respectively, compared to those of the as-fabricated LEDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report influences of a Si-doped graded superlattice (SiGSL) on device characteristics of green LEDs. </LI> <LI> Electrostatic discharge (ESD) characteristics of green LEDs were significantly improved by using the SiGSL. </LI> <LI> Stable optical characteristics of green LEDs was achieved by using the SiGSL structure. </LI> </UL> </P>
Excited-state Transitions of Self-assembled InAs/InAlGaAs Quantum Dots
Kwanjae Lee,Byounggu Jo,이철로,김진수,김종수,노삼규,임재영 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.6
We report the structural and optical properties of self-assembled (SA) InAs/InAlGaAs quantum dots (QDs) embedded in an InAlGaAs matrix on InP substrates grown by a molecular-beam epitaxy. By varying the amount of the arsenic supply and deposition time, the shape of SA InAs/InAlGaAs QDs was modified to relatively round shape and the QD height was also increased from 1.07 to 2.89 nm. From the power and temperature dependence of the PL spectra, the excited-state transitions were confirmed from the SA InAs QDs with the material system of InAlGaAs-InP. This is the first observation on the clear excited-state transitions for the SA InAs/InAlGaAs QDs on InP.
이관재(Kwanjae Lee),이주훤(Joowheun Lee),이모원(Mowon Lee),박재석(Jaeseok Park) 한국정보과학회 2006 한국정보과학회 학술발표논문집 Vol.33 No.1
이동 애드 혹 네트워크는 인프라가 구축된 일반 통신 네트워크와는 달리 특정 인프라 없이 구성노드들 간 통신이 가능하며, 노드의 이동 특성으로 네트워크의 변화가 심하다. 애드 혹 네트워크 환경에 따른 적합한 경로 설정 알고리즘을 선택하고 소스 노드에서 목적지 노드로의 패킷 전송 전송 중 에러 발생 시 기존 프로토콜의 경로 재설정 방법 보다 경로 재설정 시간을 최소한으로 줄여 사라진 경로 복구를 위한 최소 지연 경로 재설정 방법 및 효율적 전송 방법을 제안한다. 일정 규모 이상의 이동 노드로 구성된 애드 혹 네트워크에서 효율적인 DSR 라우팅 프로토콜을 이용하고, 에러 발생으로 인한 경로 재설정 시 빠른 경로 복구를 위하여 소규모 네트워크 환경에서 빠른 전송 성능을 가진 AODV 라우팅 프로토콜을 이용하여 패킷 전송 지연을 최소화 하는 최소 지연 경로 재설정 및 재전송 방법을 제안한다.
Choi, Ilgyu,Lee, Kwanjae,Lee, Cheul-Ro,Lee, Joo Song,Kim, Soo Min,Jeong, Kwang-Un,Kim, Jin Soo American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.20
<P>Group III-nitride light-emitting diodes (LEDs) fabricated on sapphire substrates typically suffer from insufficient heat dissipation, largely due to the low thermal conductivities (TCs) of their epitaxial layers and substrates. In the current work, we significantly improved the heat-dissipation characteristics of an InGaN/GaN quantum-well (QW) green LED by using hexagonal boron nitride (hBN) as a heat-transfer medium. Multiple-layer hBN with an average thickness of 11 nm was attached to the back of an InGaN/GaN-QW LED (hBN-LED). As a reference, an LED without the hBN (Ref-LED) was also prepared. After injecting current, heat-transfer characteristics inside each LED were analyzed by measuring temperature distribution throughout the LED as a function of time. For both LED chips, the maximum temperature was measured on the edge n-type electrode brightly shining fabricated on an n-type GaN cladding layer and the minimum temperature was measured at the relatively dark-contrast top surface between the p-type electrodes. The hBN-LED took 6 s to reach its maximum temperature (136.1 °C), whereas the Ref-LED took considerably longer, specifically 11 s. After being switched off, the hBN-LED took 35 s to cool down to 37.5 °C and the Ref-LED took much longer, specifically 265 s. These results confirmed the considerable contribution of the attached hBN to the transfer and dissipation of heat in the LED. The spatial heat-transfer and distribution characteristics along the vertical direction of each LED were theoretically analyzed by carrying out simulations based on the TCs, thicknesses, and thermal resistances of the materials used in the chips. The results of these simulations agreed well with the experimental results.</P> [FIG OMISSION]</BR>
Han, Sangmoon,Choi, Ilgyu,Lee, Kwanjae,Lee, Cheul-Ro,Lee, Seoung-Ki,Hwang, Jeongwoo,Chung, Dong Chul,Kim, Jin Soo Springer-Verlag 2018 Journal of electronic materials Vol.47 No.2
<P>We report on the dependence of internal crystal structures on the electrical properties of a catalyst-free and undoped InAs nanowire (NW) formed on a Si(111) substrate by metal-organic chemical vapor deposition. Cross-sectional transmission electron microscopy images, obtained from four different positions of a single InAs NW, indicated that the wurtzite (WZ) structure with stacking faults was observed mostly in the bottom region of the NW. Vertically along the InAs NW, the amount of stacking faults decreased and a zinc-blende (ZB) structure was observed. At the top of the NW, the ZB structure was prominently observed. The resistance and resistivity of the top region of the undoped InAs NW with the ZB structure were measured to be 121.5 k Omega and 0.19 Omega cm, respectively, which are smaller than those of the bottom region with the WZ structure, i.e., 251.8 k Omega and 0.39 Omega cm, respectively. The reduction in the resistance of the top region of the NW is attributed to the improvement in the crystal quality and the change in the ZB crystal structure. For a field effect transistor with an undoped InAs NW channel, the drain current versus drain-source voltage characteristic curves under various negative gate-source voltages were successfully observed at room temperature.</P>