THELEDS Co.

Gwangju, South Korea

THELEDS Co.

Gwangju, South Korea
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Mun D.-H.,Chonnam National University | Bak S.J.,Chonnam National University | Ha J.-S.,Chonnam National University | Lee H.-J.,Dong - A University | And 3 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2014

In this study, we grew ZnO nanowires hydrothermally on (1-102) r-plane sapphire substrates in an aqueous solution which contained zinc nitrate hexahydrate and hexamethylenetetramine (HMT) at 90 °C. First, the AZO seed layer of 80 nm thickness was deposited on the r-plane sapphire substrate by a radio frequency magnetron sputter. After that, we grew the ZnO nanowires on the seed layer by changing the precursor concentration of the aqueous solution from 0.025 M to 0.01 M. When the molar concentration of the precursor was changed, the diameter, length, density and number of ZnO nanowires also changed significantly: diameter, length and density increased with increasing molar concentration but the number of ZnO nanowires decreased. The ZnO nanowires grown at the higher molar concentration tended to grow along with the c-axis direction, as revealed by atomic force microscope and X-ray diffraction peaks. Furthermore, the PL spectra measured at room-temperature revealed a UV emission of 380 nm which can be attributed to the radiative recombination of free and bound excitons (Near Band edge Emission). The NBE emission was also increased with increasing molar concentration. Copyright © 2014 American Scientific Publishers.


Zhao J.L.,Tianjin University | Sun X.W.,Tianjin University | Sun X.W.,Nanyang Technological University | Ryu H.,Inje University | Moon Y.B.,THELEDS Co.
Optical Materials | Year: 2011

Highly transparent conductive Ga-doped ZnO (GZO) thin films have been prepared on glass substrates by metal organic chemical vapor deposition. The effect of Ga doping on the structural, electrical and optical properties of GZO films has been systematically investigated. Under the optimum Ga doping concentration (∼4.9 at.%), c-axis textured GZO film with the lowest resistivity of 3.6 × 10-4 Ω cm and high visible transmittance of 90% has been achieved. The film also exhibits low transmittance (<1% at 2500 nm) and high reflectance (>70% at 2500 nm) to the infrared radiation. Furthermore, our developed GZO thin film can well retain the highly transparent conductive performance in oxidation ambient at elevated temperature (up to 500 °C). © 2010 Elsevier B.V. All rights reserved.


Kim T.-S.,Kongju National University | Ahn B.-J.,Kongju National University | Dong Y.,Kongju National University | Park K.-N.,Kongju National University | And 7 more authors.
Applied Physics Letters | Year: 2012

We experimentally investigated well-to-well non-uniformity in InGaN/GaN multiple quantum well (MQW) structures by using capacitance-voltage measurements with additional laser illumination. By varying the illuminating power of the resonant excitation, well-to-well non-uniformity through the MQWs was clearly revealed. The quantum wells (QWs) close to the n-GaN side show higher carrier accumulations and larger position shift as the excitation power is increased, relative to the p-side QWs. Both results were attributed to the existence of stronger piezoelectric fields in the n-side QWs induced by subsequent partial relaxation of strain through the MQWs. © 2012 American Institute of Physics.


Song J.-H.,Kongju National University | Dong Y.,Kongju National University | Kim H.-J.,Kongju National University | Ahn B.-J.,Kongju National University | And 7 more authors.
Physica Status Solidi - Rapid Research Letters | Year: 2010

We investigated the effects of a strain-control layer on piezoelectric fields and indium incorporation in blue-emitting InGaN/GaN quantum wells (QWs) using reverse-biased electroreflectance spectroscopy. With this technique, we could determine the change in both indium incorporation and the piezoelectric field by the inserted buffer layer. We compared two test samples, which have identical structures except for the insertion of an additional InGaN layer at the bottom of the blue-QW. The magnitude of the piezoelectric fields in the QWs with the added layer was significantly smaller even with a slightly higher indium composition. The result shows that the strain in the QW is partially released and can be controlled quantitatively by the strain-control layer underneath. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Dong Y.,Kongju National University | Song J.-H.,Kongju National University | Kim H.-J.,Kongju National University | Kim T.-S.,Kongju National University | And 7 more authors.
Journal of Applied Physics | Year: 2011

Raman and emission properties of a nonpolar a-plane InGaN/GaN blue-green light emitting diode (LED) on an r-sapphire substrate are investigated and compared with a conventional c-plane blue-green LED. The output power of the a-plane LED was 1.4 mW at 20 mA. The c-plane LED has higher EQE, but it reaches the maximum at a lower forward current and the droop is faster than the a-plane counterpart. As the reverse bias increased, a blueshift in the PL spectra was not observed in the a-plane structure, which is indicative of an absence of quantum confined Stark effects. However, a strong blueshift in the electroluminescence spectra was still present, which means the In localization effects are relevant in nonpolar InGaN/GaN quantum wells. In the Raman spectra, a strong anisotropy of E2(high) phonon modes was observed. By comparing the frequency of the E2(high) modes, we demonstrate that the residual compressive strain in an a-plane LED is significantly smaller than in the polar counterpart. © 2011 American Institute of Physics.


Ahn B.-J.,Kongju National University | Kim T.-S.,Kongju National University | Dong Y.,Kongju National University | Hong M.-T.,Kongju National University | And 6 more authors.
Applied Physics Letters | Year: 2012

We report the experimental determination of current spill-over in InGaN/GaN blue light emitting diodes by measuring the change in the forward current generated by a resonant excitation. To quantify accurately, the absorption of the laser as a function of the forward current was also determined. Two samples that have clearly different behavior of efficiency droop were compared to clarify the relationship between the current spill-over and the efficiency droop. We conclude that the carrier spill-over does occur and can be a significant cause for the efficiency droop but cannot single-handedly account for the efficiency droop. © 2012 American Institute of Physics.


There are provided a semiconductor substrate configured to improve the light extraction efficiency of a light emitting device, and a light emitting device using the substrate. The light emitting device includes the substrate, a buffer layer, and a light emitting structure, and the buffer layer and the light emitting structure being sequentially stacked on the substrate. The substrate includes a plurality of lenses disposed on a top surface thereof, and the lenses have a horn shape and are configured such that the buffer layer grows both on the top surface of the substrate and lateral surfaces of the lenses.


Patent
Theleds Co. | Date: 2011-05-03

A light emitting device having an electrode structure in which resistance to electrostatic discharge (ESD) is increased, the static electricity is efficiently dispersed and a current concentration phenomenon is prevented, the light emitting device including: a substrate; a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer opposite to the first conductivity type semiconductor layer that are sequentially formed on the substrate; a first conductivity type electrode pad formed on the first conductivity type semiconductor layer; a second conductivity type electrode pad formed on the second conductivity type semiconductor layer; a first auxiliary electrode formed on the second conductivity type semiconductor layer to extend in one direction and having one end connected to the second conductivity type electrode pad and the other end formed in an opposite direction to a direction toward the first conductivity type electrode pad; and a second auxiliary electrode formed on the second conductivity type semiconductor layer to extend in one direction and including a main arm having one end connected to the second conductivity type electrode pad and the other end formed in a direction toward the first conductivity type electrode pad and a plurality of second auxiliary sub-electrodes extending from the other end of the main arm, wherein a direction in which an end of each of the second auxiliary sub-electrodes extends, is not toward the first conductivity electrode pad.


Patent
Theleds Co. | Date: 2010-10-20

Provided is a light emitting diode package. The light emitting diode package includes a package body, a light emitting diode chip, and a package lens. The light emitting diode chip is installed in the package body. The package lens is installed in the package body to cover the light emitting diode chip, and is formed to have a shape corresponding to a radiation angle pattern of the light emitting diode chip.


Patent
Theleds Co. | Date: 2011-01-13

Provided is a semiconductor light emitting device having an improved electrode structure for uniform current density and high brightness. According to the present invention, an light emitting device can have an electrode structure configured to spread a current uniformly and efficiently throughout the entire area of the light emitting device. Therefore, current density distribution can be more uniform in the light emitting device. End parts of second conductive type auxiliary electrodes are gradually shortened in length in a direction away from a first conductive type electrode pad so that a current flowing around the first conductive type electrode can be uniform to increase optical conversion efficiency and lower a driving voltage.

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