Papers by Author: Won Jae Lee

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Authors: Jung Doo Seo, Joon Ho An, Jung Gon Kim, Jung Kyu Kim, Myung Ok Kyun, Won Jae Lee, Il Soo Kim, Byoung Chul Shin, Kap Ryeol Ku
Abstract: SiC single crystal ingots were prepared onto different seed material using sublimation PVT techniques and then their crystal quality was systematically compared. In this study, the conventional SiC seed material and the new SiC seed material with an inserted SiC epitaxial layer on a seed surface were used as a seed for SiC bulk growth. The inserted epitaxial layer was grown by a sublimation epitaxy method called the CST with a low growth rate of 2μm/h. N-type 2”-SiC single crystals exhibiting the polytype of 6H-SiC were successfully fabricated and carrier concentration levels of below 1017/cm3 were determined from the absorption spectrum and Hall measurements. The slightly higher growth rate and carrier concentration were obtained in SiC single crystal ingot grown on new SiC seed materials with the inserted epitaxial layer on the seed surface, maintaining the high quality.
Authors: J.H. Choi, Laurence Latu-Romain, Edwige Bano, Anne Henry, Won Jae Lee, Thierry Chevolleau, Thierry Baron
Abstract: A comprehensive study on different polytypes (α-SiC and β-SiC) and crystal orientations ((0001) and (11-20) of 6H-SiC) has been investigated in order to elaborate Silicon carbide (SiC) nanopillar using inductively coupled plasma etching method. The SiC nanopillars with the cross section of rhombus, pentagon, and hexagonal have been obtained on β-SiC (001), misoriented α-SiC (11-20), and α-SiC (0001) on-axis substrates, respectively. It was found that crystal orientations and polytypes play key roles for the morphology of SiC nanopillars, which reflects the so-called Wulff's rule.
Authors: Hee Jun Lee, Hee Tae Lee, Hee Won Shin, Mi Seon Park, Yeon Suk Jang, Won Jae Lee, Im Gyu Yeo, Tai Hee Eun, Jang Yul Kim, Myoung Chul Chun, Si Hyun Lee, Jung Gon Kim
Abstract: The effect of the porous graphite plate above the source material on properties of silicon carbide (SiC) crystals grown by Physical Vapor Transport method has been investigated. The porous graphite plate was inserted on source powder to produce a more C-rich for the polytype stability of 4H-SiC crystal and a uniform radial temperature gradient. The dendrite structure obtained from SiC source powder in the crucible with porous graphite plate was more densely formed than that in the conventional crucible. The crystal quality of 4H-SiC single crystals grown in porous graphite inserted crucible was revealed to be better than that of crystal grown SiC crystals in the conventional crucible.
Authors: Joon Ho An, Gi Sub Lee, Won Jae Lee, Byoung Chul Shin, Jung Doo Seo, Kap Ryeol Ku, Heon Decok Seo, Hae Do Jeong
Abstract: 2inch 6H-SiC (0001) wafers were sliced from the ingot grown by a conventional physical vapor transport (PVT) method using an abrasive multi-wire saw. While sliced SiC wafers lapped by a slurry with 1~9㎛ diamond particles had a mean height (Ra) value of 40nm, wafers after the final mechanical polishing using the slurry of 0.1㎛ diamond particles exhibited Ra of 4Å. In this study, we focused on investigation into the effect of the slurry type of chemical mechanical polishing (CMP) on the material removal rate of SiC materials and the change in surface roughness by adding abrasives and oxidizer to conventional KOH-based colloidal silica slurry. The nano-sized diamond slurry (average grain size of 25nm) added in KOH-based colloidal silica slurry resulted in a material removal rate (MRR) of 0.07mg/hr and the Ra of 1.811Å. The addition of oxidizer (NaOCl) in the nano-size diamond and KOH based colloidal silica slurry was proven to improve the CMP characteristics for SiC wafer, having a MRR of 0.3mg/hr and Ra of 1.087Å.
Authors: Im Gyu Yeo, Tae Woo Lee, Jong Hwi Park, Woo Sung Yang, Heui Bum Ryu, Mi Seon Park, Il Soo Kim, Byoung Chul Shin, Won Jae Lee, Tai Hee Eun, Seung Seok Lee, Myong Chuel Chun
Abstract: The single crystal ingots by using a sublimation technique were grown on 6H-SiC dual-seed crystals with opposite face polarities and then SiC crystal wafers sliced from the SiC ingot were systematically investigated to find out the polarity dependence of the crystal quality. The growth rate of the SiC crystal grown in this study was about 0.2mm/hr. N-type 2’’ SiC crystals exhibiting the 4H- and 6H-SiC polytype were successfully fabricated on C-face and Si-face, respectively. The incorporation of nitrogen donors in the SiC crystals grown on the C-face seed crystal was exhibited to be higher than in SiC crystals grown on a Si-face crystal. When the SiC crystal ingot proceeded to grow, the SiC crystal region grown on the C-face seed crystal was enlarged compared to the SiC crystal region on the Si-face seed crystal.
Authors: Hee Jun Lee, Hee Tae Lee, Hee Won Shin, Mi Seon Park, Yeon Suk Jang, Won Jae Lee, Dong Yeob Kim, Soon Ku Hong, Jung Gon Kim
Abstract: Aluminum nitride (AlN) bulk crystals, approximately 50.8mm in diameter and up to 5mm thickness, were grown by a physical vapor transport (PVT) method in a tantalum crucible. To investigate the effect of crucible materials, various crucible materials, a graphite and TaC-coated graphite and tantalum crucible were used for the AlN growth. XRD pattern of AlN crystal grown on SiC seed in the Ta-crucible exhibited only (00l) peaks, indicating that AlN single crystal was successfully grown on SiC seed. The interface structure between AlN and SiC crystals was observed by a high resolution TEM.
Authors: Tae Woo Lee, Im Gyu Yeo, Byoung Chul Shin, Won Jae Lee, Mi Seon Park, Hyun Hee Hwang, Shigehiro Nishino
Abstract: We adopted HMDS(Hexamethyledisilane) as a SiC(Silicon carbide) source material for epitaxial growth of 3C-SiC on Si substrate. Various growth profiles were investigated to optimize hetero-epitaxial growth of 3C-SiC layers. We also focused on the homogeneous film deposition of 3C-SiC on Si by employing two susceptor shapes, flat and tilted susceptors, to control a thickness of the boundary layer formed on the Si substrate. Fringe color patterns were observed on 3C-SiC layer on Si and hence it was easy to characterize the film uniformity by analyzing this color. 3C-SiC epitaxial layers were systematically analyzed by an optical microscope, a Raman spectroscopy, a SEM and an XRD.
Authors: Chi Kwon Park, Joon Ho An, Won Jae Lee, Byoung Chul Shin, Shigehiro Nishino
Abstract: A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. We aimed to systematically investigate the dependence of SiC epilayer quality and growth rate during the sublimation growth using the CST method on various process parameters such as the growth temperature and working pressure. The etched surface of a SiC epitaxial layer grown with low growth rate (30 μm/h) exhibited a low etch pit density (EPD) of ~2000 /cm2 and a low micropipe density (MPD) of 2 /cm2. The etched surface of a SiC epitaxial layer grown with a high growth rate (above 100 μm/h) contained a high EPD of ~3500 /cm2 and a high MPD of ~500 /cm2, which indicates that high growth rate aids the formation of dislocations and micropipes in the epitaxial layer.
Authors: Hyun Seung Lee, Min Jae Kim, Min Hee Kim, Sang Il Lee, Won Jae Lee, Byoung Chul Shin, Shigehiro Nishino
Abstract: The chlorinated precursor is recently focused for high growth rate and high quality epitaxial layer. In the previous studies, the addition of chlorinated species from Si2Cl6 in the gas phase eliminated simultaneous Si nucleation which interferes with epitaxy. In this work, the characterization of epitaxial layers grown with chlorinated species is focused. High growth rate of 30 μm/h was achieved by using Si2(CH3)6 and Si2Cl6 as chlorinated precursors. We concluded that high growth rate was achieved by using HMDS and HCDS as the precursor of SiC at growth temperature of 1600 °C.
Authors: G.X. Liu, F.K. Shan, Byoung Chul Shin, Won Jae Lee
Abstract: Pulsed laser deposition (PLD) technique is a very powerful method for fabricating various oxide thin films due to its native merits. In this study, gallium and nitrogen co-doped ZnO thin films (0.1 at.%) were deposited at different temperatures (100-600°C) on sapphire (001) substrates by using PLD. X-ray diffractometer, atomic force microscope, spectrophotometer, and spectrometer were used to characterize the structural, the morphological and the optical properties of the thin films. Hall measurements were also carried out to identify the electrical properties of the thin films.
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