Browsing by Author "Lin, C. H."

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Anomalous diamagnetic shift for negative trions in single semiconductor quantum dots
(2010-03-01)
Fu, Y. J.
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Lin, S. D.
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Tsai, M. F.
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Lin, H.
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Lin, C. H.
We report on the magnetic response of negative trions X(-) in single self-assembled InAs/GaAs quantum dots. Unlike the conventional quadratic diamagnetic shift for neutral excitons, the observed X(-) diamagnetic shifts are small and nonquadratic. In particular, we also observed a reversal in sign of the conventional diamagnetic shift. A theoretical analysis indicates that such anomalous behaviors for X(-) arise from an apparent change in the electron wave function extent after photon emission due to the strong Coulomb attraction induced by the hole in its initial state. This effect can be very pronounced in small quantum dots, where the electron wave function becomes weakly confined and extended much into the barrier region. When the electrons gradually lose confinement, the magnetic response of X(-) will transit gradually from the usual quadratic diamagnetic shift to a quartic dependence, and finally into a special paramagnetic regime with an overall negative energy shift.
Carrier Dynamics in InAs/GaAs Quantum Rings
(2009)
Lin, C. H.
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Ling, H. S.
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Sun, K. W.
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Lee, C. P.
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Lin, S. D.
We have investigated the temperature dependence of the carrier relaxation dynamics in InAs/GaAs self-assembled quantum rings by using the time-resolved photoluminescence technique with a time resolution of similar to 250 ps. The carrier relaxation in the QRs not only shows strong dependence on the lattice temperature, it is also significant slower than the carrier relaxation in the quantum dots at temperature above 150 K.
Crucial integration of high work-function metal gate and high-k blocking oxide on charge-trapping type flash memory device
(2008-12-22)
Tsai, Ping-Hung
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Chang-Liao, Kuei-Shu
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Yang, Dong-Wei
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Chung, Yuan-Bin
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Wang, Tien-Ko
Charge-trapping type flash memory devices with various integrations of metal gates having different work functions and blocking oxides were investigated in this work. Improved erasing speed together with acceptable reliability characteristics can be achieved by the integration of high work-function metal gate and high-k blocking oxide due to an efficient suppression of electron back tunneling through the blocking oxide during erasing operation for the MoN sample. Specifically, the high work-function value of MoN metal gate can be kept only by integrating with the Al(2)O(3) blocking oxide because it can suppress the formation of molybdenum-silicide. Moreover, high-speed erasing can also be demonstrated by combining the MoN metal gate with an HfAlO charge trapping layer when band-to-band hot hole erasing method is adopted.
Efficiency Improvement of GaN-Based LEDs With a SiO(2) Nanorod Array and a Patterned Sapphire Substrate
(2010-06-01)
Huang, H. W.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
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Hsu, H. W.
The enhancement of light extraction from GaN-based light-emitting diodes (LEDs) with a patterned sapphire substrate (PSS) and a SiO(2) 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on transistor-outline-can package, the light output powers of LED with a PSS and LED with a PSS and a SiO(2) PQC structure are enhanced by 35% and 48%, compared with the conventional LED. In addition, the higher output power of the LED with a PSS and a SiO(2) PQC structure is due to better reflectance on PSS and higher epitaxial quality on an n-GaN using a SiO(2) 12-fold PQC structure pattern. These results provide promising potential to increase output powers of commercial light-emitting devices.
Efficiency Improvement of GaN-Based LEDs With a SiO2 Nanorod Array and a Patterned Sapphire Substrate
(2010-06-01)
Huang, H. W.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
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Hsu, H. W.
The enhancement of light extraction from GaN-based light-emitting diodes (LEDs) with a patterned sapphire substrate (PSS) and a SiO2 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on transistor-outline-can package, the light output powers of LED with a PSS and LED with a PSS and a SiO2 PQC structure are enhanced by 35% and 48%, compared with the conventional LED. In addition, the higher output power of the LED with a PSS and a SiO2 PQC structure is due to better reflectance on PSS and higher epitaxial quality on an n-GaN using a SiO2 12-fold PQC structure pattern. These results provide promising potential to increase output powers of commercial light-emitting devices.
Enhanced light extraction of InGaN-based green LEDs by nano-imprinted 2D photonic crystal pattern
(2008-05-01)
Cheng, B. S.
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Chiu, C. H.
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Huang, K. J.
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Lai, C. F.
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Kuo, H. C.
In this paper, we propose a simple, low cost and mass producible nanoimprint lithography (NIL) method to texture the surface of GaN-based light emitting diodes (LEDs) with a two-dimensional photonic crystal (2DPC). Such a 2DPC structure not only enhanced the light output power but also changed the far-field pattern simultaneously. Also, a TiO(2)/SiO(2) omnidirectional reflector (ODR) was deposited on the backside of the LEDs to further increase the light output power. Under 350 mA current injection, it was found that forward voltages were 3.35, 3.34 and 3.75 V while the light output powers of the LEDs were 59.5, 92.5 and 112.1 mW for the conventional LED, the PCLED with 20 nm depth, and the PCLED with 120 nm depth all with chip size of 1 mm x 1 mm, respectively. A 88.4% enhancement in light output power of PCLED with a 120 nm depth and ODR on the backside could be achieved when compared to the conventional LED under the driving current of 350 mA. From the measurement results, it was also found that the NIL process does not degrade the electrical properties of the fabricated LEDs.
Enhanced light output from a nitride-based power chip of green light-emitting diodes with nano-rough surface using nanoimprint lithography
(2008-05-07)
Huang, H. W.
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Lin, C. H.
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Yu, C. C.
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Chiu, C. H.
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Lai, C. F.
Enhanced light extraction from a GaN-based power chip (PC) of green light-emitting diodes (LEDs) with a rough p-GaN surface using nanoimprint lithography is presented. At a driving current of 350 mA and with a chip size of 1 mm x 1 mm packaged on transistor outline (TO)-cans, the light output power of the green PC LEDs with nano-rough p-GaN surface is enhanced by 48% when compared with the same device without a rough p-GaN surface. In addition, by examining the radiation patterns, the green PC LED with nano-rough p-GaN surface shows stronger light extraction with a wider view angle. These results offer promising potential to enhance the light output powers of commercial light-emitting devices by using the technique of nanoimprint lithography under suitable nanopattern design.
Enhanced light output power of GaN-based vertical-injection light-emitting diodes with a 12-fold photonic quasi-crystal by nano-imprint lithography
(2009-08-12)
Huang, H. W.
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Lin, C. H.
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Lee, K. Y.
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Yu, C. C.
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Huang, J. K.
GaN-based thin-film vertical-injection light-emitting diodes (VLEDs) with a 12-fold photonic quasi-crystal (PQC) by nano-imprint lithography (NIL) are fabricated and presented. At a driving current of 20 mA and with a chip size of 350 mu m x 350 mu m, the light output power of our thin-film LED with a 12-fold PQC structure reaches 41 mW. This result is an enhancement of 78% when compared with the output power of a VLED without a PQC structure. In addition, the corresponding light radiation pattern shows a narrower beam shape due to the strong guided light extraction effect by the formed PQC structure in the vertical direction.
Enhanced vertical extraction efficiency from a thin-film InGaN-GaN light-emitting diode using a 2-D photonic crystal and an omnidirectional reflector
(2008-05-01)
Lin, C. H.
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Yen, H. H.
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Lai, C. F.
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Huang, H. W.
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Chao, C. H.
An InGaN-GaN thin-film vertical-type light-emitting diode with a two-dimensional photonic crystal (PC) on the emitting surface and a TiO2-SiO2 onmidirectional reflector on the bottom was fabricated. The device was investigated by performing a series of experiments and numerical computations. Electroluminescence measurement revealed a strong extraction enhancement in the vertical direction at 433-nm wavelength. The emission spectrum of the light was found to be strongly modified by the PC to have a significantly narrow linewidth of 5 nm. Our experimental results were in accord with those obtained from our numerical findings.
Enhanced vertical extraction efficiency from a thin-film InGaN/GaN photonic crystal light-emitting diodes
(2008)
Lai, Chun-Feng
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Huang, H. W.
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Lin, C. H.
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Kno, H. C.
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Lu, T. C.
An InGaN/GaN thin-film light-emitting diode with the photonic crystal (PhC) on the surface and a TiO(2)/SiO(2) omnidirectional reflector on the bottom was fabricated and found the line-width emission spectrum of 5 nm by the PhC. (C) 2007 Optical Society of America
Enhancement of InGaN-GaN indium-tin-oxide flip-chip light-emitting diodes with TiO2-SiO2 multilayer stack omnidirectional reflector
(2006-09-01)
Lin, C. H.
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Lai, C. F.
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Ko, T. S.
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Huang, H. W.
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Kuo, H. C.
Enhancement of light extraction of GaN-based flip-chip indium-tin-oxide light-emitting diodes (FC ITO LEDs) with an onmidirectional reflector (ODR) is presented. The ODR consisting of alternating layers of TiO2 and SiO2 is designed to possess a complete photonic bandgap within the blue region of interest, and it is fabricated by E-beam deposition. At a driving current of 300 mA and a chip size of 1 mm x 1 mm, the light output power of the FC ITO LEDs with the ODR reaches 156 mW. This is an enhancement of 31% when compared with the same device with an Al mirror instead. Furthermore, by examining the radiation patterns, the FC ITO LED with the ODR shows stronger enhancement around the vertical direction. Our work offers promising potential for enhancing output powers of commercial light-emitting devices.
Enhancement of InGaN/GaN flip-chip ITO LEDs with incline sidewalls coated with TiO2/SiO2 omnidirectional reflector
(2007)
Chiu, C. H.
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Kuo, H. C.
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Lai, C. F.
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Huang, H. W.
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Wang, W. C.
The light extraction enhancement of GaN-based flip-chip indium-tin oxide light-emitting diodes (FC ITO LEDs) with an inclined sidewall coated with TiO2/SiO2 omnidirectional reflectors (ODRs) is presented. At a driving current of 350 mA and a chip size of 1x1 mm, the light output power and the light extraction enhancement of the FC ITO LEDs coated TiO2/SiO2 ODRs with inclined sidewall reached 183 mW and 15% when compared with the results from the same device, FC ITO LEDs coated TiO2/SiO2 ODRs with vertical sidewall. Furthermore, by examining the radiation patterns of the FC ITO LEDs, the increased optical power within 150 degrees cone contributed to the stronger enhancement around the vertical direction of an inclined sidewall ODR within blue regime. Our work offers promising potential for enhancing output powers of commercial light-emitting devices. (c) 2007 The Electrochemical Society.
Enhancement of light output power of GaN-based light-emitting diodes using a SiO(2) nano-scale structure on a p-GaN surface
(2010-06-01)
Huang, H. W.
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Lai, F. I.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
GaN (gallium nitride)-based light-emitting diodes (LEDs) with a nano-scale SiO(2) structure between a transparent indium-tin oxide (ITO) layer and p-GaN were fabricated. The forward voltage at 20 mA for a GaN-based LED with a SiO(2) nano-scale structure was slightly higher than that of a conventional GaN-based LED because the total area of the p-type metal contact between the transparent ITO layer and p-GaN was smaller. However, the light output power for the GaN-based LED with a nano-scale structured SiO(2) at 20 mA was 24% higher than that for a conventional GaN-based LED structure. This increase in the light output power is mostly attributed to the scattering of light from the SiO(2) photonic quasi-crystal (PQC) layer.
Enhancement of light output power of GaN-based light-emitting diodes using a SiO2 nano-scale structure on a p-GaN surface
(2010-06-01)
Huang, H. W.
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Lai, F. I.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
GaN (gallium nitride)-based light-emitting diodes (LEDs) with a nano-scale SiO2 structure between a transparent indium-tin oxide (ITO) layer and p-GaN were fabricated. The forward voltage at 20 mA for a GaN-based LED with a SiO2 nano-scale structure was slightly higher than that of a conventional GaN-based LED because the total area of the p-type metal contact between the transparent ITO layer and p-GaN was smaller. However, the light output power for the GaN-based LED with a nano-scale structured SiO2 at 20 mA was 24% higher than that for a conventional GaN-based LED structure. This increase in the light output power is mostly attributed to the scattering of light from the SiO2 photonic quasi-crystal (PQC) layer.
Fabrication and characteristics of thin-film InGaN-GaN light-emitting diodes with TiO2/SiO2 omnidirectional reflectors
(2007-07-01)
Chiu, C. H.
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Kuo, H. C.
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Lee, C. E.
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Lin, C. H.
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Cheng, P. C.
In this paper, a novel GaN-based thin-film vertical injection light-emitting diode (LED) structure with a TiO2 and SiO2 omnidirectional reflector (ODR) and an n-GaN rough surface is designed and fabricated. The designed ODR, consisting of alternating TiO2 and SiO2, layers possesses a complete photonic band gap within the blue region of interest. The arrays of the conducting channels are integrated into the TiO2/SiO2 ODR structure for vertically spreading the current. Assisted by the laser lift-off and photo-enhanced chemically etched surface roughening process, the light output power and the external quantum efficiency of our thin-film LED with a TiO2/SiO2 ODR (at a driving current of 350 mA and with chip size of 1 mm x 1 mm) reached 330 mW and 26.7%, increased by 18% and 16%, respectively, compared with the results from the thin-film LED with an Al mirror. By examining the radiation patterns of the LEDs, the optical output power mainly increased within the 120 deg cone due to the higher reflectance of the TiO2/SiO2 ODR within the blue regime.
High Efficiency White LEDs with 2D Photonic Quasi-Crystal and Patterned Sapphire Substrate
(2008)
Chiu, C. H.
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Cheng, B. S.
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Kuo, H. C.
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Lu, T. C.
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Wang, S. C.
A high emitting efficiency GaN-based white LED with 2D PQC on surface and PSS were successfully fabricated. After packaging, 21% enhancement in emitting luminous flux was achieved under the driving current 20 mA. (C) 2008 Optical Society of America
High-performance GaN-based vertical-injection light-emitting diodes with TiO2-SiO2 omnidirectional reflector and n-GaN roughness
(2007-03-01)
Huang, H. W.
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Kuo, H. C.
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Lai, C. F.
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Lee, C. E.
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Chiu, C. W.
We have designed and fabricated a new type of GaN-based thin-film vertical-injection light-emitting diode (LED) with TiO2-SiO2 onmidirectional reflector (ODR) and n-GaN roughness. The associated ODR designed for LED operation wavelength at 455 nm vias integrated with patterned conducting channels for the purpose of vertical current spreading. With the help of laser lift-off and. photo-electrochemical etching technologies, at a driving current of 350 mA and with chip size of 1 mm x 1 mm, the light-output power and the external quantum efficiency of our thin-film LED with TiO2-SiO2 ODR reached 330 mW and 26.7%. The result demonstrated 18% power enhancement when compared with the results from the thin-film LED with Al reflector replace.
Improvement of light output in GaN-based power chip light-emitting diodes with a nano-rough surface by nanoimprint lithography
(2008-04-01)
Huang, H. W.
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Lin, C. H.
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Yu, C. C.
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Lee, B. D.
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Chiu, C. H.
The enhancement of light extraction of gallium nitride (GaN)-based power chip (PC) light-emitting diodes (LEDs) with a p-GaN rough surface by nanoimprint lithography (NIL) is presented. At a driving current of 350 mA and a chip size of 1 mm x 1 mm, the light output power of the PC LEDs with a p-GaN rough surface (etching depth from 130 to 150 nm) showed an enhancement of 24% on wafer when compared with the same device without NIL. Current-voltage results indicated an ohmic contact by the increase in the contact area of the nano-roughened surface at 200 mA. This paper offers a promising potential for enhancing the output powers of commercial LEDs.
Investigation of GaN-based light emitting diodes with nano-hole patterned sapphire substrate (NHPSS) by nano-imprint lithography
(2009-08-25)
Huang, H. W.
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Lin, C. H.
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Huang, J. K.
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Lee, K. Y.
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Lin, C. F.
In this paper, gallium-nitride (GaN)-based light-emitting diodes (LEDs) with nano-hole patterned sapphire (NHPSS) by nano-imprint lithography are fabricated and investigated. At an injection current of 20mA, the LED with NHPSS increased the light output power of the InGaN/GaN multiple quantum well LEDs by a factor of 1.33, and the wall-plug efficiency is 30% higher at 20mA indicating that the LED with NHPSS had larger light extraction efficiency. In addition, by examining the radiation patterns, the LED with NHPSS shows stronger light extraction with a wider view angle. These results offer promising potential to enhance the light output powers of commercial light-emitting devices using the technique of nano-imprint lithography. (C) 2009 Elsevier B.V. All rights reserved.
Investigation of GaN-based vertical-injection light-emitting diodes with GaN nano-cone structure by ICP etching
(2008-07-25)
Huang, H. W.
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Lin, C. H.
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Yu, C. C.
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Lee, K. Y.
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Lee, B. D.
The GaN-based thin-film vertical-injection LEDs (VLEDs) with GaN nano-cone structures are fabricated and presented. Under the process conditions of fixed Cl(2)/Ar now rate of 10/25sccm and ICP/bias power of 200/200W, the GaN nano-cone structures are self-assembly formed with variable density of 1.5 x 10(7) to 1.4 x 10(1) cm(-2) and variable depth of 0.56-1.34 mu m when varying the ICP chamber pressure. At a driving current of 350mA and with chip size of 1 mm x 1 mm, the light output power of our thin-film LED with a specific GaN nano-cone structure reaches 224 mW which is enhanced by 160% when compared with the output power of conventional VLED. In addition, the corresponding light radiation pattern Shows Much higher light intensity Clue to the strong light scattering effect by the formed nano-cone Structure. (C) 2008 Elsevier B.V. All rights reserved.