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패턴된 사파이어 기판 및 ITO 투명전극을 이용한 405nm 질화물계 반도체 발광다이오드의 성능 개선
한영헌,김성진,김송강,김창연,오동주,유순재,최용석 한국물리학회 2005 새물리 Vol.50 No.5
We demonstrate improvement in a of 405-nm GaN-based light-emitting diode (LED) by introducing an indium-tin-oxide (ITO) transparent metal electrode (TME) and lateral epitaxy on a patterned sapphire substrate (LEPS). The crystal defect density in the GaN epitaxial layers is noticeably decreased by growth on a patterned-sapphire substrate because the internal quantum eciency is improved. The light-output power of the 405-nm GaN-LED is also dramatically improved by changing a NiAu TME to an ITO TME. The integrated maximum light-output power of the 405-nm ITO GaN-LED is approximately 15.6 mW at a 20-mA junction current, which indicates an approximately 25.5 % external quantum eciency (EQE).
전자공명 분자선 에피택시법으로 성장한 GaN박막의 Si 불순물 첨가에 의한 Photoluminescence 개선
이용배,한영헌,유순재 선문대학교 1999 공과대학논문집 Vol.1 No.2
ECR-MBE 법으로 Al_(2)O_(3) 사파이어 기판상에 성장한 GaN의 Si 불순물 첨가에 의한 발광 특성을 조사하였다. Al_(2)O_(3) 상에 성장한 얇은 박막의 GaN는 Si 불순물을 혼입하므로서 PL 발광특성이 개선되는데 Si 분자선원의 강도 3.2×10^(-9) Torr에서 최대의 강도를 나타냈다. 이 때 성장온도는 760 ℃, Si 분자선 온도는 1100℃이었으며 SIMS를 측정하여 불순물의 농도는 2.2×10^(19) cm^(-3)임을 확인하였다. Si을 혼입하지 않은 시료에서 발광 강도는 약하게 나타나는 것은 결정 중에 존재하는 비 발광성 재결합의 활성화에 기인하며 Si의 혼입에 따라 이러한 비 발광성 재결합이 감소하는 것으로 생각하여 PL 온도 의존성 특성으로 조사하였다. Si 의 혼입은 비 발광성 재결합 에 기인하는 결함의 배위 변화 또는 결합으로 인한 비 발광성 재결합의 활성화 에너지의 증가로 해석되었다. 또 PL 스펙트럼의 온도에 따를 강도의 변화로부터 비 발광성 재결합의 활성화 에너지를 계산하였는데 Si 온도 1100℃에서 15 meV 정도의 활성화 에너지의 증가를 보였다. Improvement of luminescence by Si-doping in defective thin wurtzite GaN layer grown on (0001) sapphire using ECR-MBE was studied. The activation energy of nunradiative recombination and photoluminescence intensity was increased with Si doping concentration in the range of about 2.2×10^(19) cm^(-3). From temperature dependance of photoluminescence the increase of activation energy of nonradiative recombination center with Si concentration was evaluated. The increase of activation energy induced by the Si doping of 2.2×10^(19) cm^(-3) was estimated to be 15 meV.
최용석,김성진,한영헌,유순재,이은아,김학수,김송강,Choi, Yong-Seok,Kim, Seong-Jin,Han, Young-Heon,Yu, Soon-Jae,Lee, Eun-Ah,Kim, Hak-Soo,Kim, Song-Gang 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.6
We have investigated the excitation-light source dependence of photo-catalytic efficiency for the benzene removal. The photo-catalytic module for the benzene removal is fabricated by a combination of GaN-based ultraviolet light-emitting diode (UV GaN-LED) and $TiO_2$ thin film coated on an aluminum plate. The benzene reduction rates of 365 nm and 375 nm modules at 60 mA junction current are approximately $8.95\;\%/Hr$ and $9.2\;\%/Hr$, respectively, which indicates that 365 nm GaN-LED is more effective than 375 nm GaN-LED. The benzene reduction efficiency is also noticeably dependent on the excitation wavelength and excitation-light power, as well as it is increased with the shorter wavelength and higher excitation power. This result exhibits that UV GaN-LED is useful to remove the volatile organic compounds (VOCs) existing in the environment.
산화막 형성조건에 따른 FP-type SiC-SBD의 항복전압 의존성
김성진,오동주,한영헌,김창연,최용석,유순재 한국물리학회 2005 새물리 Vol.51 No.1
In order to fabricate a high breakdown voltage SiC-SBD (Schottky barrier diode), we investigated the dependence of the breakdown voltage on the oxidation condition in a eld plate (FP)-type SiCSBD. The reverse breakdown voltage of FP-type SiC-SBD depended signicantly on the oxide formation condition. The FP-type SiC-SBDs with a 1200-A thermal oxide and an 8000-A annealed PECVD (plasma-enhanced chemical-phase deposition) oxide showed reverse breakdown voltages of approximately 750 V and 300 V, respectively. The breakdown voltage of FP-type SiC-SBDs was found to depend on the oxide quality rather than the oxide thickness. There are two origins from the reverse breakdown phenomenon in FP-type SiC-SBDs. One is due to crystal defects, such as micropipes and stacking faults, in the SiC substrate and the epi-layer, and occurs at lower reverse voltages. The other is due to oxide demolition in the oxide overlap region, and which occurs at higher reverse voltages. The oxide demolition in the oxide overlap region is attributed to a concentration of the electric eld at high reverse voltages.