• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.414-414
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• 2013

InGaAlAs/InP은 $1.3{\sim}1.55{\mu}m$ 레이저 다이오드 응용을 위한 InGaAsP/InP를 대체하기 위한 물질로 많은 관심을 받아왔다. 디지털 합금 InGaAlAs 다중양자우물(multiple quantum wells: MQWs) 시료는 MBE (molecular beam epitaxy) 장비를 이용하여 n-InP 기판 위에 성장하였다. 양자우물과 장벽은 각각 (InGaAs)0.8(InAlAs)0.2와 (InGaAs)0.4(InAlAs)0.6 SPSs (short-period superlattices)로 $510^{\circ}C$에서 성장하였다. 발광특성을 향상시키기 위하여 질소분위기에서 $700^{\circ}C$ $750^{\circ}C$ 또는 $800^{\circ}C$에서 30초간 열처리(rapid thermal annealing: RTA)하였다. RTA 온도에 따른 디지털 합금 InGaAlAs MQWs의 발광특성을 분석하기 위해 PL (photoluminescence)과 TRPL(time-resolved PL)을 이용하였다. RTA 온도에 따른 InGaAlAs MQWs 시료의 발광 메카니즘 및 운반자 동력학을 연구하기 위하여 발광파장 및 온도에 따른 TRPL을 측정하였다. 저온(10 K)에서 PL 피크는 RTA 온도를 $700^{\circ}C$에서 $750^{\circ}C$로 증가하였을 때 1,242 nm에서 1,245 nm로 장파장 영역으로 이동하였다가 $800^{\circ}C$에서 열처리하였을 때 단파장 영역으로 이동하여 1,239 nm에서 나타났다. 또한 PL 세기는 RTA 온도를 증가함에 따라 증가함을 보이다가 RTA 온도를 $800^{\circ}C$로 증가하였을 때 PL 세기는 감소하였다. 발광소자 개발을 위한 InAlGaAs MQWs 시료의 최적의 열처리 조건을 이러한 PL과 TRPL 결과로부터 결정할 수 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.2
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• pp.61-65
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• 2024

HVPE (Hydride vapor phase epitaxy) is a method of manufacturing thin films or single crystals using gaseous raw materials. This is a method that applies the principles of chemical vapor deposition to grow a single crystal of a material with low meltability or high melting point, and is one of the methods that can obtain a gallium nitride (GaN) single crystal. Recently, much research has been conducted to grow aluminum nitride (AlN) single crystals using this method, but good results have not yet been obtained. In this study, we attempted to grow AlN single crystals using the HVPE method. Nitrogen was used as a carrier gas in the growth process, and the growth results according to changes in the amount of nitrogen (N₂) were examined. Changes in growth crystals as the amount of nitrogen increased were confirmed. The shape of the grown AlN single crystal was observed using an optical microscope, and the rocking curve was measured using double crystal X-ray diffractometry (DCXRD) to confirm the creation of the AlN crystal. The crystallinity of single crystals was also investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.20-20
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• 2003

We developed 30 ㎽-AlInGaN based violet laser diodes. The fabrication procedures of the laser diodes are described as follows. Firstly, GaN layers having very low defect density were grown on sapphire substrates by lateral epitaxial overgrowth method. The typical dislocation density was about 1-3$\times$10$^{6}$ /$\textrm{cm}^2$ at the wing region. Secondly, AlInGaN laser structures were grown on LEO-GaN/sapphire substrates by MOCVD. UV activation method, instead of conventional annealing, was conducted to achieve good p-type conduction. Thirdly, ridge stripe laser structures were fabricated. The cavity mirrors were formed by cleaving method. Three pairs of SiO$_2$ and TiO$_2$ layers were deposited on the rear facet for mirror coating. Lastly, laser diode chips were mounted on AlN submount wafers by epi-down bonding method. The lifetime of the laser diodes was over 10,000 hrs at room temperature under automatic power controlled condition. We expect the performance of the LDs to be improved by the optimization of the growth and fabrication process. The detailed characteristics and important issues of the laser diodes will be discussed at the conference.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.150-150
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• 2008

고효율 LED를 얻기 위해서는 LED의 내부 양자효율과 외부 양자효율이 높아야 한다. 현재 GaN-Based LED의 내부 양자효율은 결정의 질의 개선 및 이중이종접합 또는 다중양자우물 구조와 같이 활성층의 캐리어 농도를 높이는 접합구조로 설계되어 거의 100%에 가까워졌다. 그러나 외부 양자효율은 반도체 재료의 높은 굴절률로 인하여 외부로 탈출하지 못하고 내부로 전반사 되어 반도체 내부에 갇히게 되는데 이처럼 갇힌 빛은 반도체와 중간 Interface에 TIR(total internal reflection) 또는 반사판에 의해 계속적으로 반사 된다. 그러므로 이를 해결하기 위한 플립칩 구조, 포토닉 크리스탈 등의 여러 가지 방법들이 제시되고 있지만 아직도 더 높은 외부 양자 효율의 개선을 요구하고 있다. 본 연구에서는 새로운 형태의 반사판(Al) 즉 p-GaN과 반사판 사이의 interlayer로 반사판과의 오믹 접촉을 고려한 Embo type의 NiO를 구현하여 반사된 빛의 방향을 내부반사를 줄일 수 있는 방향으로 변화시킴으로써 광 추출 효율의 향상을 기대할 수 있게 되었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.470-475
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• 2009

We deposited $Al_2O_3$ thin films on GaN by remote plasma atomic layer deposition (RPALD) technique, trimethylaluminum(TMA) and oxygen were used as precursors, at fixed process condition, the number of cycle were changed. Growth rate per cycle was $1.2\;{\AA}$/cycle. and Growth rate was in proportion to a number of cycle, the GaN MIS capacitors that $Al_2O_3$ thin film were deposited above 12 nm, have excellent electrical properties, a low electrical leakage current density(${\sim}10^{-10}\;A/cm^2$ at 1.5 MV), but below 12 nm, we can see the degradation of the leakage current density. After post deposition annealing, Dielectric constant was estimated by 1 MHz high-frequency C-V method, it was varied with the anealing temperature from 6.9 at no post anealed to 7.6 at $800^{\circ}C$, and we can see a improvement of the leakage current density and breakdown voltage by post deposition anealing below $700^{\circ}C$, but, after anealed at $800^{\circ}C$, we can see the degradation of the leakage current density and breakdown voltage.

• Bulletin of the Korean Chemical Society
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• v.18 no.3
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• pp.311-316
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• 1997

The synthesis and characterization of the mononuclear group 13 heterocyclic carboxaldehyde methyldithiocarbazate complexes Me2M[NC5H4CRNNC(S)SCH3] (M=Al, R=H(1); M=Ga, R=H(2); M=Al, R=CH3(3); M-Ga, R=CH3(4); M=In, R=CH3(5)) are described. Compounds 1-5 were prepared by the reaction of MMe3 (M=Al, Ga, In) with 2-formy or 2-acetylpyridine-S-methyldithiocarbazate in toluene. These compounds 1-5 have been characterized by microanalysis, NMR (1H, 13C) spectroscopy, mass spectra, and single-crystal X-ray diffraction. X-ray single-crystal diffraction analyses reveal that 4-5 are mononuclear metal compounds with coordination number of 5 and N,N,S coordination mode.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.3-26
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• 1999

We have successfully grown <111>-oriented (La,Sr)(Al,Ta)$O_3$(LSAT) mixed-perovskite single crystals and <0001>-oriented $Ca_8La_2(PO_4)_6O_2$(CLPA) single crystals with the apatite structure by the Czochralski method. The compositional and lattice parameter uniformity of the crystals are discussed in relation to the growth conditions. Since LSAT and CLPA single crystals have excellent lattice matching with GaN, they ar promising as new substrates for the growth of high quality GaN epitaxial layers.

• Applied Microscopy
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• v.30 no.4
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• pp.337-345
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• 2000

Introduction of the buffer layer and the nitridation of a sapphire substrate were one of the most general methods employed for the reduction of lattice defects in GaN thin films Brown on sapphire by MOCVD. In an effort to improve the initial nucleation and growth condition of the GaN, reactive ion beam (RIB) of nitrogen treatment of the sapphire surface has been attempted. The 10 nm thick, amorphous $AlO_xN_y$ layer was formed by RIB and was partially crystallized alter the main growth of GaN at high temperature, leaving isolated amorphous regions at the interface. The beneficial effect of amorphous layer at interface in relieving the thermal stress between substrate and GaN film was examined by measuring the lattice strain value of the GaN film grown with and without the RIB treatment. Higher order Laue zone pattern (HOLZ) of $[\bar{2}201]$ zone axis was compared with simulated patterns and lattice strain was estimated It was confirmed that the great reduction of thermal strain was achieved by RIB process and the amount of thermal stress was 6 times higher in the GaN film grown by conventional method without the RIB treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.93-93
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• 1998

III-V족 질화물반도체를 이용한 광 및 전자소자 용용에 있어서 가장 중요한 고홈위 u undoped GaN 에피충 성장과 GaN 에피충의 doping 특허 p-type doping의 복성융 고찰한다. 그리고 III-V nitride 이용한 band gap en명neertng에 있어서 가장 중요한 InGaN 생장파 81 및 :at codoplng 륙성융 평가 분석 한다. 위의 기반기술융 기본으로 하여 InGaN/AlG때 DH s$\sigma$ucture lED훌 제작하고 이의 륙성 용 명가분석하였다.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.1
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• pp.13-20
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• 2021

GaN has shown good potential owing to its better chemical stability than other materials and tunable bandgap with materials such as InN and AlN. Tunable bandgap allows GaN to make the maximum utilization of the solar spectrum, thus improves the solar-to-hydrogen (STH) efficiency. In addition, GaN band gap contains the oxidation and reduction level of water, so it can split water without external voltage. However, STH efficiency using GaN itself is low and has been actively studied recently to improve it. In this thesis, we have summarized the studies related to the use of GaN as a photoelectrode for photoelectrochemical water splitting.