C.-H. Kwak
Pohang University of Science and Technology
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Publication
Featured researches published by C.-H. Kwak.
Applied Physics Letters | 2010
C.-H. Kwak; Byungsub Kim; Chang-In Park; S.-Y. Seo; S.H. Kim
Vertically-well-aligned ZnO nanorods were synthesized on Ti buffer layers by a metal-organic chemical-vapor deposition process. Structural analyses demonstrated that the ZnO nanorods were well-aligned in the c-axis and ab-plane. Transmission electron microscopy (TEM) showed that the Ti buffer layer was amorphous and interdiffused into the ZnO nanorods. Energy-dispersive spectroscopy (EDS) analysis revealed the Ti buffer layers to be slightly oxide. Extended x-ray absorption fine structure confirmed the TEM and EDS results. The I-V characteristic measurements showed a 20-fold increase in current density with the Ti buffer layer, suggesting excellent electrical contact between the Ti buffer layer and ZnO nanorods.
Applied Physics Letters | 2016
Woo-Young Jung; Jae-Bok Seol; C.-H. Kwak; Chan-Gyung Park
The compositional distribution of In atoms in InGaN/GaN multiple quantum wells is considered as one of the candidates for carrier localization center, which enhances the efficiency of the light-emitting diodes. However, two challenging issues exist in this research area. First, an inhomogeneous In distribution is initially formed by spinodal decomposition during device fabrication as revealed by transmission electron microscopy. Second, electron-beam irradiation during microscopy causes the compositional inhomogeneity of In to appear as a damage contrast. Here, a systematic approach was proposed in this study: Electron-beam with current density ranging from 0 to 20.9 A/cm2 was initially exposed to the surface regions during microscopy. Then, the electron-beam irradiated regions at the tip surface were further removed, and finally, atom probe tomography was performed to run the samples without beam-induced damage and to evaluate the existence of local inhomegenity of In atoms. We proved that after eliminating the electron-beam induced damage regions, no evidence of In clustering was observed in the blue-emitting InGaN/GaN devices. In addition, it is concluded that the electron-beam induced localization of In atoms is a surface-related phenomenon, and hence spinodal decomposition, which is typically responsible for such In clustering, is negligible for biaxially strained blue-emitting InGaN/GaN devices.
Journal of Crystal Growth | 2012
S.-Y. Seo; C.-H. Kwak; Sungjoo Kim; S.-H. Park; I.-J. Lee; Seung-A Han
Journal of the Korean Physical Society | 2008
S.-H. Park; Y.-B. Lee; C.-H. Kwak; S.-Y. Seo; S.H. Kim; Yong-Dae Choi
Journal of Crystal Growth | 2010
S.-Y. Seo; C.-H. Kwak; Sungjoo Kim; Byung-Hyuk Kim; Chan-Hee Park; S.-H. Park; Seung-A Han
Journal of Crystal Growth | 2011
C.-H. Kwak; Byung-Hyuk Kim; Chang-In Park; S.-Y. Seo; Sungjoo Kim
Journal of Crystal Growth | 2009
C.-H. Kwak; Byung-Hyuk Kim; S.-H. Park; S.-Y. Seo; Chan-Hee Park; Sungjoo Kim; Seung-A Han
Current Applied Physics | 2011
C.-H. Kwak; Y.-B. Lee; S.-Y. Seo; Sungjoo Kim; Chan-Hee Park; Byung-Hyuk Kim; D.W. Jeong; Jongyoon Kim; Zhenlan Jin
Journal of the Korean Physical Society | 2008
S.-Y. Seo; C.-H. Kwak; Y.-B. Lee; S.H. Kim; S.-H. Park
Journal of Nanoscience and Nanotechnology | 2011
C.-H. Kwak; Y.-B. Lee; S.-Y. Seo; S.H. Kim; Chan-Hee Park; Byungwhan Kim; Zhenlan Jin