Browsing by Author "Kuo, H. -C."

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Defect selective passivation in GaN epitaxial growth and its application to light emitting diodes
(2009-11-23)
Lo, M. -H.
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Tu, P. -M.
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Wang, C. -H.
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Cheng, Y. -J.
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Hung, C. -W.
A defect selective passivation method to block the propagation of threading dislocations in GaN epitaxial growth is demonstrated. The defect selective passivation is done by using defect selective chemical etching to locate defect sites, followed by silicon oxide passivation of the etched pits, and epitaxial over growth. The threading dislocation density in the regrown epilayer is significantly improved from 1x10(9) to 4x10(7) cm(-2). The defect passivated epiwafer is used to grow light emitting diode and the output power of the fabricated chip is enhanced by 45% at 20 mA compared to a reference one without using defect passivation.
Electrically driven nanoarrow array green LED
(2012)
Chang, J. -R.
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Chang, S. -P.
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Chen, Y. -C.
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Sou, K. -P.
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Cheng, Y. -J.
An electrically driven nanopyramid green light emitting diode (LED) was demonstrated. The nanopyramid arrays were fabricated from a GaN substrate by patterned nanopillar etch, pillar side wall passivation, and epitaxial regrowth. Multiple quantum wells were selectively grown on the facets of the nanopyramids. The fabricated LED emits green wavelength under electrical injection. The emission exhibits a less carrier density dependent wavelength shift and higher internal quantum efficiency as compared with a reference c-plane sample at the same wavelength. It shows a promising potential for using nanopyramid in high In content LED applications.
Electrically driven nanopyramid green light emitting diode
(2012-02-06)
Chang, S. -P.
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Chen, Y. -C.
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Huang, J. -K.
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Cheng, Y. -J.
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Chang, J. -R.
An electrically driven nanopyramid green light emitting diode (LED) was demonstrated. The nanopyramid arrays were fabricated from a GaN substrate by patterned nanopillar etch, pillar side wall passivation, and epitaxial regrowth. Multiple quantum wells were selectively grown on the facets of the nanopyramids. The fabricated LED emits green wavelength under electrical injection. The emission exhibits a less carrier density dependent wavelength shift and higher internal quantum efficiency as compared with a reference c-plane sample at the same wavelength. It shows a promising potential for using nanopyramid in high In content LED applications. (C) 2012 American Institute of Physics. [doi:10.1063/1.3681363]
Energy Efficient 850 nm Vertical-Cavity Surface-Emitting Lasers with Extremely Low Driving-Current Density for > 40 Gbit/sec Error-Free Transmissions from RT to 85 degrees C
(2015)
Chi, Kai-Lun
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Jiang, Jia-Wei
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Yen, Jia-Liang
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Lu, I-Cheng
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Kuo, H. -C.
850nm VCSELs with record-low driving-current-density (8kA/cm(2)) small resistance (6012), wide-bandwidth (26GHz), and small energy-to-data-rate ratio (228fJ/bit; 3.5mA) for >41Gbit/sec error-free transmission over 100 (2) meter OM4 fiber at room-temperature (85 degrees C) have been demonstrated. (C) 2014 Optical Society of America
Enhanced electron-hole plasma stimulated emission in optically pumped gallium nitride nanopillars
(2011-03-21)
Lo, M. -H.
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Cheng, Y. -J.
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Kuo, H. -C.
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Wang, S. -C.
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光電工程學系
An enhanced stimulated emission was observed in optically pumped GaN nanopillars. The nanopillars were fabricated from an epitaxial wafer by patterned pillar etching followed by crystalline regrowth. Under optical excitation, a strong redshifted stimulated emission peak emerged from a broad spontaneous emission background. The emission is attributed to the electron-hole plasma gain at high carrier density. The emission slope efficiency was greatly enhanced by 20 times compared with a GaN substrate under the same pumping condition. The enhancement is attributed to the better photon and gain interaction from the multiple scattering of photons among nanopillars. (C) 2011 American Institute of Physics. [doi:10.1063/1.3570634]
Fabrication and luminescent properties of core-shell InGaN/GaN multiple quantum wells on GaN nanopillars
(2012-06-25)
Chang, J. -R.
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Chang, S. -P.
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Li, Y. -J.
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Cheng, Y. -J.
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Sou, K. -P.
Core-shell InGaN/GaN multiple quantum wells (MQWs) on GaN nanopillars were fabricated by top-down etching followed by epitaxial regrowth. The regrowth formed hexagonal sidewalls and pyramids on the nanopillars. The cathodoluminescence of MQWs blue shifts as the location moves from top to bottom on both the pillar sidewalls and pyramid facets, covering a spectral linewidth of about 100 nm. The MQWs on the pillar sidewalls have a higher InN fraction than those on the pyramid facets. The photoluminescent wavelength is stable over two orders of carrier density change due to the smaller quantum confined Stark effect on the nanopillar facets. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731629]
GaN-based vertical-cavity surface emitting lasers with sub-milliamp threshold and small divergence angle
(2016-12-12)
Yeh, P. S.
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Chang, C. -C.
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Chen, Y. -T.
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Lin, D. -W.
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Liou, J. -S.
A GaN-based vertical-cavity surface emitting laser (VCSEL) structure featuring a silicon-diffusion-defined current blocking layer for lateral confinement is described. Sub-milliamp threshold currents were achieved for both 3- and 5-mu m-aperture VCSELs under continuous-wave operation at room temperature. The vertical cavity was defined by a top dielectric distributed Bragg reflector (DBR) and a bottom epitaxial DBR. The emission spectrum exhibited a single peak at 411.2 nm with a line-width of 0.4nm and a side mode suppression ratio of more than 10 dB before device packaging. The full-width-at-half-maximum divergence angle of the 3-mu m-aperture VCSEL was as small as approximately 5 degrees which is the lowest number reported. These results implied the 3-mu m-aperture VCSEL was in near single-mode operation. Published by AIP Publishing.
Hybrid photonic crystal light-emitting diode renders 123% color conversion effective quantum yield
(2016-05-20)
Krishnan, C.
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Brossard, M.
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Lee, K. -Y.
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Huang, J. -K.
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Lin, C. -H.
Colloidal quantum dots (QDs) have emerged as promising color conversion light emitters for solid-state lighting applications [Nat. Photonics 7, 13 (2012) due to their emission tunability and near-unity photoluminescence quantum yields. In the current commercial LEDs, QDs are dispersed into an encapsulation layer in a far-field architecture, where the majority of the light emitted by the LED remains trapped within the epitaxy due to total internal reflection, drastically reducing the out-coupling efficiency. In this paper, we demonstrate a photonic quasi-crystal hybrid LED geometry that allows QD emitters to be placed in close proximity to the multiple quantum wells (MQWs) of the active area. This architecture greatly improves the coupling between MQWs and QDs, simultaneously allowing for a non-radiative resonant energy transfer between the MQWs and the QDs and near-field radiative coupling of trapped ( guided) modes in the LED to the emitters. In this configuration, we demonstrate record-breaking effective quantum yields reaching 123% for single-color conversion LEDs and 110% for white light-emitting devices. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article\'s title, journal citation, and DOI.
Numerical study of optical properties of InGaN multi-quantum-well laser diodes with polarization-matched AlInGaN barrier layers
(2009-04-01)
Chen, J. -R.
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Ling, S. -C.
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Huang, H. -M.
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Su, P. -Y.
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Ko, T. -S.
The optical properties of InGaN multi-quantum-well laser diodes with different polarization-matched AlInGaN barrier layers have been investigated numerically by employing an advanced device simulation program. The use of quaternary polarization-matched AlInGaN barrier layers enhances the electron-hole wave function overlap due to the compensation of polarization charges between InGaN quantum well and AlInGaN barrier layer. According to the simulation results, it is found that, among the polarization-matched quantum-well structures under study, lower threshold current and higher slope efficiency can be achieved simultaneously when the aluminum composition in AlInGaN barrier layers is about 10-15%. The optimal polarization-matched InGaN/AlInGaN laser diode shows lower threshold current and higher slope efficiency compared to conventional InGaN/InGaN laser diodes.
Phosphor-free GaN-based transverse junction light emitting diodes for the generation of white light
(2006-11-01)
Shi, J. -W.
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Huang, H. -Y
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Wang, C. -K.
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Sheu, J. -K.
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Lai, W. -C.
We demonstrate a GaN-based phosphor-free near-white-light light-emitting-diode (LED) structure that operates in the visible wavelengths and offers broadening and flattening optical bandwidth performance. The incorporation of GaN-based dual wavelengths (blue and green) multiple-quantum-wells with a transverse p-n junction produces a device which can directly generate stable and near visible white-light emissions. The shape of the optical spectra (440-560 nm) are invariable from low to very high levels of bias currents. The problems of nonuniform carrier distribution and bias dependent electrolumineseence. spectra that occur in traditional phosphor-free white-light or near-white-light LEDs (with vertical p-n junctions) are eliminated by the demonstrated structure.