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InGaN/GaN MQW Nanorods LED Fabricated by ICP-RIE and PEC Oxidation Processes
(2007-01-01)
Lai, Fang-, I
;
Huang, H. W.
;
Chiu, Ching-Hua
;
Lai, C. F.
;
Lu, T. C.
The InGaN/GaN nanorods LED was successfully fabricated by ICP-RIE and PEC processes. Compared with as-grown sample, the PL and EL peak-wavelengths of the nanorods with PEC show 8.6 and 10.5 nm blue-shift, respectively. (c) 2007 Optical Society of America
Reduction of Efficiency Droop in Semipolar (1(1)over-bar01) InGaN/GaN Light Emitting Diodes Grown on Patterned Silicon Substrates
(2011-01-01)
Chiu, C. H.
;
Lin, D. W.
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Lin, C. C.
;
Li, Z. Y.
;
Kuo, H. C.
The semi-polar InGaN-based LEDs exhibits low efficiency droop because the reduction of the polarization field not only made the band diagram smoother but also restricted electron overflow to the p-GaN layer as shown in simulations. (C) 2010 Optical Society of America
Efficiency enhancement of UV/blue light emitting diodes via nanoscaled epitaxial lateral overgrowth of GaN on a SiO2 nanorod-array patterned sapphire substrate
(2008-11-15)
Chiu, C. H.
;
Li, Zhen-Yu
;
Chao, C. L.
;
Lo, M. H.
;
Kuo, H. C.
High-quality GaN layer was successfully grown on a SiO2 nanorod-array patterned sapphire substrate (NAPSS) using metal-organic chemical vapor deposition by a nanoscaled epitaxial lateral overgrowth (NELO) method. From tunneling electron microscope images, well coalescence and turned dislocations are parallel to the surface direction were clearly observed. The Raman shift measurement shows the residual stress in GaN was greatly reduced from 1.359 to 0.652 GPa when compared to a GaN on flat sapphire substrate. Also, a high-efficiency GaN-based light-emitting diodes (LEDs) were demonstrated on the NELO NAPSS GaN, the respective output power and external quantum efficiency of the NELO NAPSS LEDs were estimated to be 22 mW and 40.2% at an injection current of 20 mA, showing an enhancement factor of 52% over conventional LEDs. The significant improvement resulted from both the enhanced light extraction assisted by the NAPSS, and the reduced dislocation densities using the NELO method. (c) 2008 Published by Elsevier B.V.
Characteristics of a-plane GaN with the SiNx insertion layer grown by metal-organic chemical vapor deposition
(2008-11-15)
Ko, T. S.
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Wang, T. C.
;
Huang, H. M.
;
Chen, J. R.
;
Chen, H. G.
We utilized in-situ-grown SiNx insertion layers to mitigate part of dislocations stretching in nonpolar a-plane GaN films using metal-organic chemical vapor deposition. Both X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements revealed that better crystal quality and smoother surface could be obtained when the in-situ SiNx layer was inserted closer to the r-plane sapphire substrate and indicated that the in-situ SiNx insertion layer could suppress dislocations caused by lattice mismatch between the sapphire and epitaxial layers. In addition, photoluminescence and cathodoluminescence measurements confirmed the effect of the in-situ SiNx insertion layer on the optical properties of the improved a-plane GaN thin film, which is consistent with the XRD and AFM analyses and suggested reduction in the density of nonradiative centers. (C) 2008 Elsevier B.V. All rights reserved.
Optical characteristics of a-plane ZnO/Zn0.8Mg0.2O multiple quantum wells grown by pulsed laser deposition
(2010-10-01)
Ko, T. S.
;
Lu, T. C.
;
Zhuo, L. F.
;
Wang, W. L.
;
Liang, M. H.
We reported optical properties of a-plane ZnO/ZnMgO multiple quantum wells (MQWs) structure grown by the pulse laser deposition system. The emission peak energy of a-plane ZnO/ZnMgO MQWs kept invariant in the power-dependent photoluminescence (PL) measurement, indicating the nonpolar characteristics due to the lack of built-in electric fields. Large exciton binding energy of 68 meV was deduced and no apparent S-curve appeared in temperature-dependent PL results, demonstrating less carrier localization effect in a-plane ZnO/ZnMgO MQWs. Large difference in electronic transition levels of 45 meV due to the valence band splitting was observed in the polarization dependent absorption spectrum. Furthermore, the high degree of polarization of 92% and 56% at 20 and 300 K in PL emission of a-plane ZnO/ZnMgO MQWs were obtained. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488898]
Characteristics of emission polarization in a-plane nanorods embedded with InGaN/GaN multiple quantum wells
(2010-09-15)
Li, J. C.
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Lu, T. C.
;
Huang, H. M.
;
Chan, W. W.
;
Kuo, H. C.
Nonpolar (a-plane) GaN nanorod arrays with embedded In(x)Ga(1-x)N/GaN (x=0.09, 0.14, 0.24, and 0.30) multiple quantum wells (MQWs) grown on r-plane sapphire have been fabricated successfully by self-assembled Ni nanomasks and subsequent inductively coupled plasma reactive-ion etching. After nanorod fabrications, the polarization ratio of the emission from MQWs with lower indium composition (x=0.09 and 0.14) slightly decreases but apparently increases by at most 79% for the samples with higher indium composition (x=0.24 and 0.30). Competition between the effect of multiple scattering, strain relaxation and reduction in localized centers, expected in a-plane MQW samples, are attributed to the variations in the polarization ratios after the nanorod formation. (c) 2010 American Institute of Physics. [doi:10.1063/1.3483239]
Improving Light Output Power of the GaN-Based Vertical-Injection Light-Emitting Diodes by Mg+ Implanted Current Blocking Layer
(2009-05-01)
Tsai, Min-An
;
Yu, Peichen
;
Chen, J. R.
;
Huang, J. K.
;
Chiu, C. H.
A method for forming a current blocking layer (CBL) by ion implantation in GaN-based vertical-injection light-emitting diodes (VI-LEDs) was proposed. It was found that the use of CBL in VI-LEDs can effectively reduce the current crowding effect and enhance the light output power. The uniform emission intensity distribution of VI-LEDs with CBL was demonstrated by electroluminescence measurements. Experimental results show that the wall-plug efficiency was enhanced by 12.3% at an injection current of 20 mA, compared to that of VI-LEDs without CBL, and by 56.2% compared to that of conventional LEDs. The device simulation results reveal that the current path can be blocked by CBL, resulting in high light extraction efficiencies and large current densities within the effective emission region of active layers.
Growth and characterization of a-plane AlxGa1-xN alloys by metalorganic chemical vapor deposition
(2010-03-01)
Huang, H. M.
;
Ling, S. C.
;
Chen, J. R.
;
Ko, T. S.
;
Li, J. C.
The non-polar a-plane AlxGa1-xN alloys on GaN epitaxial layer with different Al compositions (0 <= x <= 0.2) were grown on r-plane (1 (1) over bar 0 2) sapphire substrates by using low-pressure metalorganic chemical vapor deposition (MOCVD) and the Al composition x were estimated from the X-ray diffraction measurements. According to the result of asymmetric X-ray reciprocal space mapping, AlGaN layer was coherently strained to the underlying GaN template. The a-plane AlGaN alloy with relatively lower Al composition showed a flat surface with reduction of pits. The best mean roughness of the surface morphology was 1.18 nm. The photoluminescence (PL) result revealed that the PL peak position shifted from 3.42 to 3.87 eV with 0 <= x <= 0.2. Apart from the shifted peak position with increasing Al content, the PL emission intensity and surface morphology of the a-plane AlGaN alloy with relatively low Al content show slightly better characteristics than that of the a-plane GaN and AlGaN with higher Al composition. (C) 2010 Elsevier B.V. All rights reserved.
Recent progress on GaN-based vertical cavity surface emitting lasers
(2007-01-01)
Lu, T. C.
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Kao, C. C.
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Huang, G. S.
;
Kuo, H. C.
;
Wang, S. C.
We report the recent progress of GaN-based VCSELs with two different laser structures. One is a hybrid cavity structure comprised an epitaxial AlN/GaN DBR, an InGaN/GaN MQW active region and a top dielectric DBR. Another is a dielectric cavity structure comprised an InGaN/GaN MQW layer sandwiched by two dielectric DBRs. Both lasers achieved laser action under optical pumping at the room temperature with narrow linewidth. The detailed characteristics of VCSELs will be reported. The status of the electrically pumped VCSEL will also be presented.
High Enhancement in Light Output of InGaN-based Micro-hole Array LEDs by Photoelectrochemical (PEC) Oxidation
(2008-01-01)
Lai, Fang-, I
;
Lin, S. G.
;
Hsieh, C. E.
;
Kuo, H. C.
;
Lu, T. C.
InGaN micro-hole-array LEDs (mu-LEDs) with and without oxide-film on it were fabricated. Compared with conventional LED, output power of mu-LEDs without and with oxide film have enhancement of 38% and 82% at 20 mA, respectively. (C)2008 Optical Society of America

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