• 한국전기전자재료학회논문지
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• 제32권3호
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• pp.192-195
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• 2019

Single-crystal diamond obtained by chemical vapor deposition (CVD) exhibits great potential for use in next-generation power devices. Low defect density is required for the use of such power devices in high-power operations; however, plastic deformation and lattice strain increase the dislocation density during diamond growth by CVD. Therefore, characterization of the dislocations in CVD diamond is essential to ensure the growth of high-quality diamond. In this work, we analyze the characteristics of the dislocations in CVD diamond through synchrotron white beam X-ray topography. In estimate, many threading edge dislocations and five mixed dislocations were identified over the whole surface.

• ETRI Journal
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• 제43권5호
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• pp.909-915
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• 2021

GaAs on Si grown via metalorganic chemical vapor deposition is demonstrated using various Si substrate thicknesses and three types of dislocation filter layers (DFLs). The bowing was used to measure wafer-scale characteristics. The surface morphology and electron channeling contrast imaging (ECCI) were used to analyze the material quality of GaAs films. Only 3-㎛ bowing was observed using the 725-㎛-thick Si substrate. The bowing shows similar levels among the samples with DFLs, indicating that the Si substrate thickness mostly determines the bowing. According to the surface morphology and ECCI results, the compressive strained indium gallium arsenide/GaAs DFLs show an atomically flat surface with a root mean square value of 1.288 nm and minimum threading dislocation density (TDD) value of 2.4×10⁷ cm^-2. For lattice-matched DFLs, the indium gallium phosphide/GaAs DFLs are more effective in reducing the TDD than aluminum gallium arsenide/GaAs DFLs. Finally, we found that the strained DFLs can block propagate TDD effectively. The strained DFLs on the 725-㎛-thick Si substrate can be used for the large-scale integration of GaAs on Si with less bowing and low TDD.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.424-427
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• 2003

We have investigated the microstructural analysis of epitaxial lateral overgrowth (ELO), pendeoepitaxy (PE), and superlattice structures used as technology for the reduction of structural defects like dislocation in nitride semiconductors using transmission electron microscopy. We confirmed that the regrowth process such as ELO and PE is very effective technique on the reduction of threading dislocation (less than $10^6/cm^2$) in the specific area. However, to decrease the defect density in the whole nitride films and the suppress the generation of defect by regrowth, we should find the optimized conditions. Besides, the process using double PE and AlGaN/GaN superlattice structure showed no effect on the defect reduction up to now.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.105-106
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• 1998

Evaluation of def3ects by etch-ppit formation was studied. A NaOH(30 mol%) etchant was found useful for etch-ppit developpment on ZnSe-based eppilayers grown on (001) gaAs. And a H3ppO4(85 mol%) was used in order to developp etch-ppits on GaN-base eppilayers grown on (0001) Al2O3 After etch-ppit formation on the surfsce. Transmission Electron Microscoppy(TEM) was cppmdicted. By etch-ppit developpment and TEM observation we could determine the defect typpes by etch-ppit configurfations and found origin of etch-ppit in the cse of ZnSe-based materials. Based uppon these results we can do defect identification by etch-ppit test simpply. In the case of GaN-based materials we could evaluate nanoppippe density. however high density of threading dislocations in GaN eppilayers were not revealed by etch-ppit developpment. Based uppon these results we can evaluate the nanoppippe density which difficult to evaluate using TEM beacause of its small size(diameter). And at ppresent status direct matching of etch-ppit density to dislocation density would make severe mistake.

• 한국전기전자재료학회논문지
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• 제18권6호
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• pp.582-586
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• 2005

We have grown GaN layers with in-situ SiN mask by metal organic chemical vapor deposition (MOCVD) and study the physical properties of the GaN layer. We have also investigate the effect of the SiN mask on its optical property. By inserting a SiN mask, (102) the full width at half maximum (FWHM) decreased from 480 arcsec to 409 arcsec and threading dislocation (TD) density decreased from $3.21\times10^9\;cm^{-2}\;to\;9.7\times10^8\;cm^{-2}$. The PL intensity of GaN with SiN mask improved 2 times to that without SiN mask. We have thus shown that the SiN mask improved significantly the physical and optical properties of the GaN layer.

• 한국결정성장학회지
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• 제2권2호
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• pp.53-62
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• 1992

SOI구조 형성을 위항 대용융 재결정(ZMR) 공정에서 타원형의 반사경을 기울여 빔강도분포를 인위적으로 변화시켜 실리콘 박막을 재결정시켰다. 비대칭 선형가열 효과를 해석하기 위하여 전산모사를 행하여 응고계면 근처에서의 온도분포와 열구배 변화를 조사하였다. 상부집속열원의 경사각이 증가할수록 액상의 과냉도와 실리콘 박막내의 결함열 간격은 증가하였다. 주된 결함은 연속적인 아결정립계였고 결함밀도가 낮은 경우는 isolated threading dislocations만이 관찰되었다. 단면 TEM과 박막 XRD 분석결과 실리콘 박막은 (100) 집합조직을 갖는 단결정 박막으로 재결정되었음을 확인할 수 있었다.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.125-129
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• 2016

In this study, we have investigated a high-temperature AlN nucleation layer and AlGaN epilayers on c-plane sapphire substrate by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). High resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscope (SEM) and Raman scattering measurements have been exploited to study the crystal quality, surface morphology, and residual strain of the HT-AlN nucleation layer. These analyses reveal that the insertion of an LT-AlN nucleation layer can improve the crystal quality, smooth the surface morphology of the HT-AlN nucleation layer and further reduce the threading dislocation density of AlGaN epifilms. The mechanism of inserting an LT-AlN nucleation layer to enhance the optical properties of HT-AlN nucleation layer and AlGaN epifilm are discussed from the viewpoint of driving force of reaction in this paper.

• 한국전기전자재료학회논문지
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• 제18권10호
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• pp.945-949
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• 2005

We have grown GaN layers with in-situ SiN mask by metal organic chemical vapor deposition (MOCVD) and study the physical properties of the GaN layer. We have also fabricate PN junction light emitting diode (LED) to investigate the effect of the SiN mask on its optical property By inserting a SiN mask, (102) the full width at half maximum (FWHM) decreased from 480 arcsec to 409 arcsec and threading dislocation (TD) density decreased from $3.21{\times}10^9\;cm^{-2}$ to $9.7{\times}10^8\;cm^{-2}$. The output power of the LED with a SiN mask increased from 198 mcd to 392 mcd at 20 mA. We have thus shown that the SiN mask improved significantly the physical and optical properties of the GaN layer.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권3호
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• pp.199-205
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• 2006

Patterned sapphire substrates (PSS) were fabricated by a simple wet etching process with $SiO_2$ stripe masks and a mixed solution of $H_2SO_4$ and $H_3PO_4$. GaN layers were epitaxially grown on the PSS under the optimized 2-step growth condition of metalorganic vapor deposition. During the 1st growth step, GaN layers with triangular cross sections were grown on the selected area of the surface of the PSS, and in the 2nd growth step, the GaN layers were laterally grown and coalesced with neighboring GaN layers. The density of threading dislocations on the surface of the coalesced GaN layer was $2{\sim}4\;{\times}\;10^7\;cm^{-2}$ over the entire region. The epitaxial structure of near-UV light emitting diode (LED) was grown over the GaN layers on the PSS. The internal quantum efficiency and the extraction efficiency of the LED structure grown on the PSS were remarkably increased when compared to the conventional LED structure grown on the flat sapphire substrate. The reduction in TD density and the decrease in the number of times of total internal reflections of the light flux are mainly attributed due to high level of scattering on the PSS.

• Current Optics and Photonics
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• 제1권4호
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• pp.358-363
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• 2017

In this study, we present a detailed investigation of luminescence properties of a blue light-emitting diode using InGaN/GaN (indium component is 17.43%) multiple quantum wells as the active region grown on patterned sapphire substrate by low-pressure metal-organic chemical vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman scattering (RS) and photoluminescence (PL) measurements are employed to study the crystal quality, the threading dislocation density, surface morphology, residual strain existing in the active region and optical properties. We conclude that the crystalline quality and surface morphology can be greatly improved, the red-shift of peak wavelength is eliminated and the superior blue light LED can be obtained because the residual strain that existed in the active region can be relaxed when the LED is grown on patterned sapphire substrate (PSS). We discuss the mechanisms of growing on PSS to enhance the superior luminescence properties of blue light LED from the viewpoint of residual strain in the active region.