Browsing by Author "Kao, C. C."

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Blue GaN-based vertical cavity surface emitting lasers by CW current injection at 77K
(2009)
Kuo, H. C.
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Chen, S. W.
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Kao, T. T.
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Kao, C. C.
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Chen, J. R.
In the paper, we describe the fabrication and performance characteristics of GaN-based vertical-cavity surface-emitting lasers (VCSELs) by optical pumping and current injection. According to the employment of high-quality and high-reflectivity AlN/GaN DBRs in the whole structure, the lasing action of optically pumped GaN-based VCSELs with hybrid mirrors has been observed at room temperature. Due to the excellent results of optically pumped GaN-based VCSELs with hybrid mirrors, we further demonstrated the lasing behavior of GaN-based VCSELs by continuous-wave current injection at 77 K. The laser has one dominated blue wavelength located at 462 nm with a linewidth of about 0.15 nm and the threshold injection current at 1.4 mA. The divergence angle and polarization ratio of the GaN-based VCSELs with hybrid mirrors are about 11.7 degrees and 80 %, respectively. A larger spontaneous coupling efficiency of about 7.5x10(-2) was also measured.
Fabrication of InGaN/GaN nanorod light-emitting diodes with self-assembled Ni metal islands
(2007-11-07)
Chiu, C. H.
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Lu, T. C.
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Huang, H. W.
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Lai, C. F.
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Kao, C. C.
We report the fabrication of InGaN/GaN nanorod light-emitting diodes (LEDs) using inductively coupled plasma reactive-ion etching (ICP-RIE) and a photo-enhanced chemical (PEC) wet oxidation process via self-assembled Ni nanomasks. An enhancement by a factor of six times in photoluminescence (PL) intensities of nanorods made with the PEC process was achieved in comparison to that of the as-grown structure. The peak wavelength observed from PL measurement showed a blue shift of 3.8 nm for the nanorods made without the PEC oxidation process and 8.6 nm for the nanorods made with the PEC oxidation process from that of the as-grown LED sample. In addition, we have demonstrated electrically pumped nanorod LEDs with the electroluminescence spectrum showing more efficiency and a 10.5 nm blue-shifted peak with respect to the as-grown LED sample.
Ground settlement trough due to DOT shield tunneling
(2014-01-01)
Fang, Y. S.
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Huang, M. Y.
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Liu, C.
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Kao, C. C.
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交大名義發表
In this paper, the tunneling with a Double-O-Tube (DOT) shield for the construction of Taoyuan International Airport Access Mass Rapid Transit in Taiwan was introduced. The DOT shield machine and tunneling operation was summarized. Based on the field data, it was found the backfill grouting rate decreased with increasing tunnel depth. This was probably due to: at a deeper location, the pressure to close the tail void was greater, therefore high backfill grouting rate was hard to achieve. Eleven sets of field data collected from six cases indicated that, the maximum settlement due to DOT shield tunneling decreased with increasing tunnel depth. It was also found that the width of settlement trough increased with increasing tunnel depth.
Improvement of InGaN/GaN light emitting diode performance with a nano-roughened p-GaN surface by excimer laser-irradiation
(2006-10-10)
Huang, Hung-Wen
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Kao, C. C.
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Chu, J. T.
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Liang, W. D.
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Kuo, H. C.
In this paper, we reported the InGaN/GaN light emitting diode (LED) with a nano-roughened top p-GaN surface which caused by KrF excimer laser-irradiation. Comparing with the conventional LED, the brightness of InGaN/GaN light emitting diode (LED) was raised by a factor of 1.25 at 20 mA after KrF excimer laser-irradiation (250 mJ cm(-2) at 248 nm for 25 ns). Meanwhile, the operation voltage of InGaN/GaN LED was reduced from 3.55 to 3.3 V at 20 mA with 29% reduction in the series resistance. The causes for the brightness increase can be attributed to laser-irradiation induced nano-roughening of p-GaN surface. The reduction in the series resistance can be attributed to the increased contact area of nano-roughened surface and higher hole concentration after laser-irradiation. (c) 2005 Published by Elsevier B.V.
Micro-Photoluminescence from a Single InGaN-based Nano-Pillar Fabricated by Focused Ion Beam Milling
(2008)
Yen, H. H.
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Chiu, C. H.
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Yu, Peichen
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Kao, C. C.
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Lin, C.
Micro-photoluminescence from GaN/InGAN multiple quantum wells embedded in a nano-pillar structure with a diameter of 300nm is characterized. The emission spectrum shows a blue shift of 68.3 meV in energy due to strain relaxation. (c) 2008 Optical Society of America
Optically and electrically pumped GaN-based VCSELs
(2007)
Lu, T. C.
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Kao, C. C.
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Huang, G. S.
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Kuo, H. C.
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Wang, S. C.
We report the recent progress of GaN-based VCSELs with a hybrid cavity structure comprised an epitaxial AlN/GaN DBR with superlattice insertion layers, an InGaN/GaN MQW active region and a top dielectric DBR. The lasers achieved laser action under optical pumping at the room temperature with a narrow linewidth. The preliminary results of the electrically pumped VCSEL will also be presented.
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.
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Kuo, H. C.
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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.
Recent progress on GaN-based vertical cavity surface emitting lasers - art. no. 67660G
(2007)
Lu, T. C.
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Kao, C. C.
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Huang, G. S.
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Kuo, H. C.
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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.
Strain relaxation induced microphotoluminescence characteristics of a single InGaN-based nanopillar fabricated by focused ion beam milling
(2008-08-25)
Yu, Peichen
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Chiu, C. H.
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Wu, Yuh-Renn
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Yen, H. H.
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Chen, J. R.
A freestanding nanopillar with a diameter of 300 nm and a height of 2 mu m is demonstrated by focused ion beam milling. The measured microphotoluminescence (mu-PL) from the embedded InGaN/GaN multiple quantum wells shows a blueshift of 68 meV in energy with a broadened full width at half maximum, similar to 200 meV. Calculations based on the valence force field method suggest that the spatial variation of the strain tensors in the nanopillar results in the observed energy shift and spectrum broadening. Moreover, the power-dependent mu-PL measurement suggests that the strain-relaxed emission region exhibits a higher radiative recombination rate than that of the strained region, indicating potential for realizing high-efficiency nanodevices in the UV/blue wavelength range. (C) 2008 American Institute of Physics.