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Park S.-J.,Gwangju Institute of Science and Technology | Han S.-H.,Gwangju Institute of Science and Technology | Han S.-H.,Samsung | Cho C.-Y.,Gwangju Institute of Science and Technology | And 7 more authors.
Applied Physics Letters | Year: 2010

We report on Mg doping in the barrier layers of InGaN/GaN multiple quantum wells (MQWs) and its effect on the properties of light-emitting diodes (LEDs). Mg doping in the barriers of MQWs enhances photoluminescence intensity, thermal stability, and internal quantum efficiency of LEDs. The light output power of LEDs with Mg-doped MQW barriers is higher by 19% and 27% at 20 and 200 mA, respectively, than that of LEDs with undoped MQW barriers. The improvement in output power is attributed to the enhanced hole injection to well layers in MQWs with Mg-doped barriers. © 2010 American Institute of Physics. Source


Lee K.-H.,Gwangju Institute of Science and Technology | Kim S.-M.,Korea Photonics Technology Institute KOPTI | Jeong H.,Gwangju Institute of Science and Technology | Pak Y.,Gwangju Institute of Science and Technology | And 10 more authors.
Advanced Materials | Year: 2013

All-solution-processed transparent thin film transistors (TTFTs) are demonstrated with silver grid source/drain electrodes, which are fabricated by printing and subsequent silver nanoparticles solution coating, which allows continuous processing without using high vacuum systems. The silver grid electrode shows a reasonable transmittance in visible range, moderate electrical conductance and mechanical strength. The TTFTs are employed to drive liquid crystal cells and demonstrate a successful switching operation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kim S.-M.,Korea Photonics Technology Institute KOPTI | Lee K.-H.,Gwangju Institute of Science and Technology | Jung G.Y.,Gwangju Institute of Science and Technology
CrystEngComm | Year: 2013

We fabricated InxGa1-xN multiple quantum well (MQW) light-emitting diodes (LEDs) on an air void embedded SiO2 mask using a simple process (silver (Ag) deposition, SiO2 capping, and high-temperature annealing). Ag was volatilized in the MOCVD process and formed an air void, as revealed by energy dispersive X-ray spectroscopy images. The light output power (at 20 mA) of the LED using epitaxial lateral overgrowth on the SiO2 mask (47.8%) and LED with the air void embedded SiO 2 mask (96.8%) are enhanced compared to conventional LEDs. From reflectance measurements, the enhancement of LEDs with an air void embedded SiO2 mask could be mainly explained by the increased high incident angle specular reflectance. © 2013 The Royal Society of Chemistry. Source


Seo T.H.,Chonbuk National University | Lee K.J.,Chonbuk National University | Park A.H.,Chonbuk National University | Hong C.-H.,Chonbuk National University | And 8 more authors.
Optics Express | Year: 2011

We report GaN-based near ultraviolet (UV) light emitting diode (LED) that combines indium tin oxide (ITO) nanodot nodes with two-dimensional graphene film as a UV-transparent current spreading electrode (TCSE) to give rise to excellent UV emission efficiency. The light output power of 380 nm emitting UV-LEDs with graphene film on ITO nanodot nodes as TCSE was enhanced remarkably compared to conventional TCSE. The increase of the light output power is attributed to high UV transmittance of graphene, effective current spreading and injection, and texturing effect by ITO nanodots. © 2011 Optical Society of America. Source


Son H.,Chonnam National University | Lee J.K.,Chonnam National University | Kim S.-M.,Korea Photonics Technology Institute KOPTI
Applied Physics Express | Year: 2013

GaN-InGaN vertical-injection light-emitting diodes (VLEDs) having SiO 2 nanorod arrays were demonstrated to enhance the light extraction efficiency and light propagation to the side of the LEDs. The full width at half maximum (FWHM) of the radiation patterns of the VLED having a nano-extractor (115-117°) was more extracted than that of conventional VLED (108-110°). Furthermore, the light output power of the VLEDs having nanorods was enhanced by 7.9% compared with that of the conventional VLEDs. Based on the measured far-field radiation patterns, the nanorods suppressed the total internal reflection and extracted the light to the side of the thin-GaN LEDs. © 2013 The Japan Society of Applied Physics. Source

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