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Koike, Kayo,Lee, Seogwoo,Cho, Sung Ryong,Park, Jinsub,Lee, Hyojong,Ha, Jun-Seok,Hong, Soon-Ku,Lee, Hyun-Yong,Cho, Meoung-Whan,Yao, Takafumi IEEE 2012 Photonics Technology Letters Vol.24 No.6
<P>Four types of GaN-based light-emitting diodes (LEDs) with V-pits formed in different regions were grown by metal–organic chemical vapor deposition. The position of the V-pits embedded in the layers of the LED structures was controlled by varying the growth temperature. We achieved the highest output power and lowest leakage current values with the LED structures comprising V-pits embedded in active regions and the p-GaN textured surface. The V-pit formation enhances the light output power and reverse voltage values by 1.3 times the values of the conventional LED owing to the enhancement of the light scattering probability and the effective filtering of threading dislocations.</P>
이현재,하준석,Hyo-Jong Lee,Seogwoo Lee,Meoungwhan Cho,T. Yao,김진교,홍순구,장지호 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.6
The effect of refined nitridation of sapphire substrates on the characteristics of GaN layers subsequently grown by using hydride vapor phase epitaxy (HVPE) was investigated. When low-temperature-grown (LTG) GaN buffer layers were grown on nitridated sapphire substrates in a refined way, the structural characteristics of the LTG GaN layers were found to be transferred to the subsequent high-temperature-grown (HTG) GaN layers. This result implies that well-controlled nitridation of sapphire substrates plays an important role and that the quality of the HTG GaN layer can be rationally controlled by monitoring the characteristics of a LTG GaN buffer layer when it is grown on a properly nitridated sapphire substrate.
Structural Investigation of GaN Nanograins Nucleated on a Sapphire Substrate
Chinkyo Kim,이현재,Meoungwhan Cho,Seogwoo Lee 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
The structural characteristics of GaN layers nucleated by Ga-assisted nitridation on an Al2O3 (0001) substrate were investigated by using atomic force microscopy (AFM) and synchrotron X-ray scattering. The nitridation was carried out by exposing an sapphire substrate in a quartz reactor to NH3 and Ga vapor carried by N2. The AFM images of the surface morphology for the samples showed that the mean height and width of the GaN grains formed on the substrate had a strong dependence on the growth temperature. Particularly, for the sample grown at 600 C with a mean width of 50 ± 5 nm, the specular reflectivity obtained through the (002) Bragg peak revealed that the nucleated GaN layers consisted of strained and fully relaxed layers. A detailed analysis of the X-ray scattering data showed that the 4.5 ± 0.3-nm-thick GaN layers were compressively strained and highly coherent with the substrate, but that approximately 17-nm-thick fully relaxed layers were relatively disordered in orientation. From the combined results of AFM and X-ray rocking curve measurements, we could conclude that fully relaxed nanograins were grown on top of highly strained GaN layers, not directly on top of the sapphire substrate.
Kwang Hyeon Baik,Yong Gon Seo,Soon-Ku Hong,Seogwoo Lee,Jaebum Kim,Ji-Su Son,Sung-Min Hwang IEEE 2010 IEEE photonics technology letters Vol.22 No.9
<P>We report on the effects of basal stacking faults (BSFs) on the electrical anisotropy and the device characteristics of nonpolar a-plane GaN (1120) light-emitting diodes (LEDs) on r-plane (1102 ) sapphire substrates. The sheet resistance in the direction parallel to the c-axis [0001] is 18%-70% higher than the one in the direction parallel to the m-axis [1100 ]. The anisotropic conductivity of faulted a-plane GaN films can be explained by carrier scatterings from BSFs. It is also shown that the output power of nonpolar a-plane GaN LEDs are significantly influenced by the presence of BSFs, which laterally hampers the carrier transport in the n-GaN layer, especially in the direction parallel to the c-axis in faulted nonpolar nitride films.</P>
Sung-Min Hwang,Kwang Hyeon Baik,Jae-Hyoun Park,이성호,송후영,Seogwoo Lee,Junggeun Jhin,정탁,김지현 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4
Nonpolar a-plane (11-20) InGaN/GaN light-emitting diodes were successfully demonstrated on rplane (1-102) sapphire substrates. High-crystalline-quality a-plane (11-20) GaN films with smooth morphologies were obtained by using metalorganic chemical vapor deposition (MOCVD) with a multi-step growth method. No apparent blueshift in the peak emission wavelength was observed over a 150 mA current range from on-wafer measurements, indicating that there is no strong polarizationinduced electric field in the a-plane GaN LEDs. The optical output power and the external quantum efficiency were measured as 1.3 mW and 2.55%, respectively, at a driving current of 20 mA when packaged with resin epoxy molding.
Anticancer effect of propranolol in ovarian cancer cells regardless of platinum sensitivity
( Jungyeob Seoung ),( Youngmo Kang ),( Minjung Kim ),( Minhyun Baek ),( Sujin Kim ),( Chaechun Rhim ),( Seogwoo Lee ),( Young-han Park ) 대한산부인과학회 2016 대한산부인과학회 학술대회 Vol.102 No.-
목적: To overcome the chemoresistance is the problem of treatment in ovarian cancer. To see the anticancer effect of propranolol in vitro is our purpose. 방법: We used two ovarian cancer cell lines-SKOV3 and NIHOVCA-3 cells. One is platinum sensitive and the other one is resistant to platinum. We used the propranolol to the cell proliferation assay of ovarian cancer cells. Notch1 receptor signaling was examined by notch receptor expression and hes1 gene and protein expressions. 결과: Propranolol suppressed the proliferation of both cells. The notch expression and signaling were decreased by propranolol also. 결론: Clinical application of propranolol to anticancer therapy is worth to be evaluated.