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Yongin, South Korea

Seo Y.G.,Korea Electronics Technology Institute | Seo Y.G.,Yonsei University | Baik K.H.,Korea Electronics Technology Institute | Song K.-M.,Korea Advanced Nano Fab Center | And 5 more authors.
Current Applied Physics | Year: 2010

Non-polar a-plane (1120) light-emitting diodes (LEDs) in InGaN/GaN multiple quantum well structures were successfully fabricated by metal organic chemical vapor deposition (MOCVD) directly grown on r-plane (1120) sapphire substrates. The full width at half maximums (FWHMs) of the X-ray rocking curve (XRC) of an a-plane GaN template along the c- and m-axes were measured to be ∼349 and ∼533 arcsec, respectively. The optical output power and external quantum efficiency (EQE) at drive currents of 20 mA and 100 mA under direct current operation in on-wafer measurements were 1.24 mW, 2.4% and 100 mA, 1.7%, respectively. The a-plane LED showed 2.8 nm blue shift with change in drive current from 5 mA to 100 mA. The polarization ratio at room temperature was 0.4 and it indicates that the a-plane LED has polarization anisotropy. © 2010 Elsevier B.V. All rights reserved. Source


Baik K.H.,Korea Electronics Technology Institute | Seo Y.G.,Korea Electronics Technology Institute | Hong S.-K.,Chungnam National University | Lee S.,Wavesquare Inc. | And 3 more authors.
IEEE Photonics Technology Letters | Year: 2010

We report on the effects of basal stacking faults (BSFs) on the electrical anisotropy and the device characteristics of nonpolar a-plane GaN (112̄0) light-emitting diodes (LEDs) on r-plane (11̄02) 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 [11̄00]. 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. © 2010 IEEE. Source


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. Source


Baik K.H.,Korea Electronics Technology Institute | Park J.-H.,Korea Electronics Technology Institute | Lee S.-H.,Korea Electronics Technology Institute | Song H.,Korea Electronics Technology Institute | And 5 more authors.
Journal of the Korean Physical Society | Year: 2010

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. Source


Patent
Dowa Electronics Materials Co. and Wavesquare Inc. | Date: 2011-05-12

A method for manufacturing a vertically structured Group III nitride semiconductor LED chip includes a first step of forming a light emitting structure laminate; a second step of forming a plurality of separate light emitting structures by partially removing the light emitting structure laminate to partially expose the growth substrate; a third step of forming a conductive support, which conductive support integrally supporting the light emitting structures; a fourth step of separating the growth substrate by removing the lift-off layer; and a fifth step of dividing the conductive support between the light emitting structures thereby singulating a plurality of LED chips each having the light emitting structure. A first through-hole is formed to open in a central region of each of the light emitting structures such that at least the lift-off layer is exposed, and an etchant is supplied from the first through-hole in the fourth step.

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