Browsing by Author "Lee, Chia-Yu"

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A Study of Mechanical Lift-Off Technology for High-Efficiency Vertical LEDs Using Micro-Porous GaN Template
(2013-01-01)
Lee, Chia-Yu
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Lin, Da-Wei
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Liu, Che-Yu
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Hsu, Shih-Chieh
;
Kuo, Hao-Chung
The high efficiency vertical light emitting diodes (V-LEDs) using mechanical lift-off with Micro-Porous GaN template formed by high temperature molten KOH wet etching process were demonstrated. The average threading dislocation density (TDD) of u-GaN after regrowth was estimated by transmission electron microscopy (TEM) reduced from 2x10(9) to 1x10(8) cm(2). The sapphire substrate was easily removed by mechanical lift-off during wafer bonding process. The light output of V-LEDs are greatly enhanced by 100% compared with Conventional-LEDs at an operating current of 20mA due to the high quality thin GaN and excellent heating dissipation.
Additional Refresh Technology (ART) of advanced-MVA(AMVA) mode for high quality LCDs
(2007)
Huang, Yi-Pai
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Huang, Wei-Kai
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Tsao, Cheng-Han
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Su, Jeng-Jia
;
Hou, Hong-Lung
We proposed "Additional Refresh Technology(ART)", which has the features of low color washout and fast response speed by only modifying the pixel layout. Besides, by utilizing ART technology, the image can be real time optimized with simple method. ART have succesfully been implemented as the Advanced-MV4 (AMVA) mode for AUO's LCD-TV products, that ART has become the promising solution of advanced LCD-TV panels for mass-production.
Analysis and application of an on-package planar inverted-F antenna
(2007-06-01)
Ling, Ching-Wei
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Lee, Chia-Yu
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Tang, Chia-Lun
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Chung, Shyh-Jong
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電信工程研究所
An on-package planar inverted-F antenna (PIFA is -described. The on-package PIFA consists of a single folded metal plate and has several advantages, including small size, light weight, low cost, and ease of fabrication. The antenna radiation pattern is omnidirectional in the H-plane. The coupling effect between the on-package PIFA and the radio-frequency (RF) components in the shielding package was studied. The antenna performance rarely changes and the isolation between the antenna and the RF components can be maximized when the locations of the components are appropriately arranged in the package. Finally, a wireless local-area network (WLAN) front-end module (FEM) including the switch, low-pass filter (LPF), bandpass filter (BPF), and power amplifier (PA), is embedded into the shielding package of the antenna. The error vector magnitude (EVM) of the resultant antenna integrated FEM, together with a WLAN card containing the baseband/medium-access control (MAC) circuitry, is tested. Good performance is obtained, showing the usability of the proposed antenna configuration.
Effect of InGaN/GaN Multiple Quantum Wells with p-n Quantum Barriers on Efficiency Droop in Blue Light-emitting Diodes
(2013-01-01)
Wang, Sheng-Wen
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Lin, Da-Wei
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Lee, Chia-Yu
;
Liu, Che-Yu
;
Lan, Yu-Pin
In this study, the structures of InGaN/GaN multiple quantum wells (MQWs) with p-n quantum barriers in various positions were proposed to investigate the efficiency droop behavior for blue light-emitting diodes (LEDs). The simulated electric field diagrams showed that the quantum well (QW) sandwiched by the p-n quantum barriers had a less electric field than the other QWs due to the original polarization-related electric field was partially balanced off by the built-in electric field of the p-n quantum barriers. In addition, the simulation results demonstrated that by selecting suitable position of p-n quantum barriers, the distribution of carriers could be effectively improved; hence the droop behavior could also be suppressed.
Efficiency and droop improvement in green InGaN/GaN light-emitting diodes on GaN nanorods template with SiO2 nanomasks
(2012-12-03)
Lin, Da-Wei
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Lee, Chia-Yu
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Liu, Che-Yu
;
Han, Hau-Vei
;
Lan, Yu-Pin
This study presents the green InGaN/GaN multiple quantum wells light-emitting diodes (LEDs) grown on a GaN nanorods template with SiO2 nanomasks by metal-organic chemical vapor deposition. By nanoscale epitaxial lateral overgrowth, microscale air voids were formed between nanorods and the threading dislocations were efficiently suppressed. The electroluminescence measurement reveals that the LEDs on nanorods template with SiO2 nanomasks suffer less quantum-confined Stark effect and exhibit higher light output power and lower efficiency droop at a high injection current as compared with conventional LEDs. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768950]
Efficiency droop behavior improvement through barrier thickness modification for GaN-on-silicon light-emitting diodes
(2015-03-05)
Tzou, An-Jye
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Lin, Bing-Cheng
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Lee, Chia-Yu
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Lin, Da-Wei
;
Liao, Yu-Kuang
Crack-free GaN-based light-emitting diodes (LEDs) were grown on 150-mm-diameter Si substrates by using low-pressure metal-organic chemical vapor deposition. The relationship between the LED devices and the thickness of quantum barriers (QBs) was investigated. The crystal quality and surface cracking of GaN-on-Si were greatly improved by an AlxGa1-xN buffer layer composed of graded Al. The threading dislocation density of the GaN-on-Si LEDs was reduced to < 7 x 10(8) cm(-2), yielding LEDs with high internal quantum efficiency. Simulation results indicated that reducing the QB thickness improved the carrier injection rate and distribution, thereby improving the droop behavior of the LEDs. LEDs featuring 6-nm-thick QBs exhibited the lowest droop behavior. However, the experimental results showed an unanticipated phenomenon, namely that the peak external quantum efficiency (EQE) and light output power (LOP) gradually decreased with a decreasing QB thickness. In other words, the GaN-on-Si LEDs with 8-nm-thick QBs exhibited low droop behavior and yielded a good peak EQE and LOP, achieving a 22.9% efficiency droop and 54.6% EQE. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate
(2014-09-16)
Lee, Chia-Yu
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Tzou, An-Jye
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Lin, Bing-Cheng
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Lan, Yu-Pin
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Chiu, Ching-Hsueh
The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 x 10(7) cm(-2) to 2.6 x 10(7) cm(-2). Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.
Enhanced Light Output Power and Growth Mechanism of GaN-Based Light-Emitting Diodes Grown on Cone-Shaped SiO2 Patterned Template
(2013-04-01)
Lin, Da-Wei
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Huang, Jhih-Kai
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Lee, Chia-Yu
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Chang, Ruey-Wen
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Lan, Yu-Pin
In this study, we successfully transferred the patterns of a cone-shaped patterned sapphire substrate (CPSS) into SiO2 layer to fabricate a cone-shaped SiO2 patterned template by using nanoimprint lithography (NIL). The GaN-based light-emitting diodes (LEDs) were grown on this template by metal-organic chemical vapor deposition (MOCVD). The transmission electron microscopy (TEM) images suggest that the stacking faults formed near the cone-shaped SiO2 patterns during the epitaxial lateral overgrowth (ELOG) can effectively suppress the threading dislocations, which results in an enhancement of internal quantum efficiency. The Monte Carlo ray-tracing simulation reveals that the light extraction efficiency of the LED grown on cone-shaped SiO2 patterned template can be enhanced as compared with the LED grown on CPSS. As a result, the light output power of the LED grown on cone-shaped SiO2 patterned template outperformed the LED grown on CPSS.
Enhancing Performance in Thin Tilm Transistors with Vacuum or Solution Processed Amorphous Oxide Semiconductors Towards Display Applications
(2018-01-01)
Chen, Changdong
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Li, Gongtan
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Li, MinMin
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Yang, Bo-Ru
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Liu, Chuan
To simultaneously achieve high mobility and good reliability of thin-film transistors (TFTs), we controlled oxygen vacancies via nitrogen incorporation in InGaZnO TFTs from vacuum-or solution-based methods. For display applications, IGZO and crystalline silicon TFTs were integrated together to build hybrid CMOS. Also, additive patterning method is developed for solution-processed oxide semiconductors, based on which wafer-scale TFT arrays and NMOS have been demonstrated.
High Reflectance Patterned Substrate Designed for Optical Devices
(2015)
Lan, Yu-Pin
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Wu, Yung-Chi
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Lin, Da-Wei
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Hong, Kuo-Bin
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Lee, Chia-Yu
This article proposed an approach by using patterned sapphire substrate to act as a 2-dimensional distributed Bragg reflector (DBR) mirror to increase the output power of LEDs.
High-Efficiency and Crack-Free InGaN-Based LEDs on a 6-inch Si (111) Substrate With a Composite Buffer Layer Structure and Quaternary Superlattices Electron-Blocking Layers
(2014-05-01)
Li, Zhen-Yu
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Lee, Chia-Yu
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Lin, Da-Wei
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Lin, Bing-Cheng
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Shen, Kun-Ching
In this paper, a composite buffer layer structure (CBLS) with multiple AlGaN layers and grading of Al composition/u-GaN1/(AlN/GaN) superlattices/u-GaN2 and InAlGaN/AlGaN quaternary superlattices electron-blocking layers (QSLs-EBLs) are introduced into the epitaxial growth of InGaN-based light-emitting diodes (LEDs) on 6-inch Si (111) substrates to suppress cracking and improve the crystalline quality and emission efficiency. The effect of CBLS and QSLs-EBL on the crystalline quality and emission efficiency of InGaN-based LEDs on Si substrates was studied in detail. Optical microscopic images revealed the absence of cracks and Ga melt-back etching. The atomic force microscopy images exhibited that the root-meansquare value of the surface morphology was only 0.82 nm. The full widths at half maxima of the (0002) and (1012) reflections in the double crystal X-ray rocking curve were similar to 330 and 450 arcs, respectively. The total threading dislocation density, revealed by transmission electron microscopy, was <6 x 10(8) cm(-2). From the material characterizations, described above, blue and white LEDs emitters were fabricated using the epiwafers of InGaNbased LEDs on 6-inch Si substrates. The blue LEDs emitter that comprised blue LEDs chip and clear lenses had an emission power of 490 mW at 350 mA, a wall-plug efficiency of 45% at 350 mA, and an efficiency droop of 80%. The white LEDs emitter that comprised blue LEDs chip and yellow phosphor had an emission efficiency of similar to 110 lm/W at 350 mA and an efficiency droop of 78%. These results imply that the use of a CBLS and QSLs-EBL was found to be very simple and effective in fabricating high-efficiency InGaN-based LEDs on Si for solid-state lighting applications.
Improvement of carrier distribution by using thinner quantum well with different location
(2014-01-01)
Wang, Sheng-Wen
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Lin, Da-Wei
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Lee, Chia-Yu
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Lin, Chien-Chung
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Kuo, Hao-Chung
We use thinner-quantum well to improve the droop behavior of GaN-base light emitting diode in simulation. Taking the advantage of that the thin quantum well will saturate easily, this characteristic of thin well will improve carrier distribution. Furthermore, this structure has more wave-function overlap than that of the thick well. This simulation result showed that decreasing the well thickness in specific position will not only improve the holes transport but also increase the quantum efficiency at high current density in the active region, and the efficiency droop behavior can be effectively suppressed. In this research, we designed three thin well structures by inserting different numbers of thin wells in the active region. We have compared them to the conventional LEDs, for which, the well thickness of 2.5 nm is used. The thin well structures have better droop behavior than conventional LED.
Improvement of emission uniformity by using micro-cone patterned PDMS film
(2014-02-24)
Liu, Che-Yu
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Chen, Kuo-Ju
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Lin, Da-Wei
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Lee, Chia-Yu
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Lin, Chien-Chung
Micro-patterned PDMS film was fabricated and combined with LED chip on board (COB) package to improve the emission uniformity of LED chip. The micro scale patterned sapphire substrate (PSS) was used as a mold to fabricate micro-cone patterned PDMS (MC-PDMS) film. A strong scattering effect from this MC-PDMS film can be verified by the high haze ratio and the Bi-directional Transmission effect. The angle dependent color temperature measurement system was used to measure the Delta CCT of COB with and without MC-PDMS. The measurement results indicate that the Delta CCT was reduced from 1025K to 428K. This improvement can effectively eliminate the yellow ring effect of LED chip. This technology can be thus considered as a cost-effective way for the next generation of light source packages. (C) 2014 Optical Society of America
Light Extraction Enhancement of GaN-Based Light-Emitting Diodes Using Crown-Shaped Patterned Sapphire Substrates
(2012-07-15)
Chiu, Ching-Hsueh
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Hsu, Lung-Hsing
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Lee, Chia-Yu
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Lin, Chien-Chung
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Lin, Bo-Wen
In this letter, we report the high performance GaN-based light-emitting diodes (LEDs) with embedded air void array grown by metal-organic chemical vapor deposition. The donut-shaped air void was formed at the interface between crown-shaped patterned sapphire substrates (CPSS) and the GaN epilayer by conventional photolithography. The transmission electron microscopy images demonstrate that the threading dislocations were significantly suppressed by epitaxial lateral overgrowth (ELOG). The Monte Carlo ray-tracing simulation reveals that the light extraction of the air-voids embedded LED was dramatically increased due to a strong light reflection and redirection by the air voids.
Microchannel Wetting for Controllable Patterning and Alignment of Silver Nanowire with High Resolution
(2015-09-30)
Yang, Bo-Ru
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Cao, Wu
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Liu, Gui-Shi
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Chen, Hui-Jiuan
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Noh, Yong-Young
Patterning and alignment of conductive nanowires are essential for good electrical isolation and high conductivity in various applications. Herein a facile bottom-up, additive technique is developed to pattern and align silver nanowires (AgNWs) by manipulating wetting of dispersions in microchannels. By forming hydrophobic/hydrophilic micropatterns down to 8 mu m with fiuoropolymer (Cytop) and SiO2, the aqueous AgNW dispersions with the optimized surface tension and viscosity self-assemble into microdroplets and then dry to form anisotropic AgNW networks. The alignment degree characterized by the full width at half-maximum (FWHM) can be well-controlled from 39.8 degrees to 84.1 degrees by changing the width of microchannels. A mechanism is proposed and validated by statistical analysis on AgNW alignment, and a static model is proposed to guide the patterning of general NWs. The alignment reduced well the electrical resistivity of AgNW networks by a factor of 5 because of the formation of efficient percolation path for carrier conduction.
Natural substrate lift-off technique for vertical light-emitting diodes
(2014-04-01)
Lee, Chia-Yu
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Lan, Yu-Pin
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Tu, Po-Min
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Hsu, Shih-Chieh
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Lin, Chien-Chung
Hexagonal inverted pyramid (HIP) structures and the natural substrate lift-off (NSLO) technique were demonstrated on a GaN-based vertical light-emitting diode (VLED). The HIP structures were formed at the interface between GaN and the sapphire substrate by molten KOH wet etching. The threading dislocation density (TDD) estimated by transmission electron microscopy (TEM) was reduced to.1 x 10(8) cm(-2). Raman spectroscopy indicated that the compressive strain from the bottom GaN/sapphire was effectively released through the HIP structure. With the adoption of the HIP structure and NSLO, the light output power and yield performance of leakage current could be further improved. (C) 2014 The Japan Society of Applied Physics
Nitrogen-Doped Amorphous InZnSnO Thin Film Transistors With a Tandem Structure for High-Mobility and Reliable Operations
(2016-05)
Li, GongTan
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Yang, Bo-Ru
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Liu, Chuan
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Lee, Chia-Yu
;
Wu, Yuan-Chun
The threshold voltage shift (Delta V-th) in amorphous InZnSnO thin-film transistors (a-IZTO TFTs) during negative gate-bias stress (NGBS) is significantly improved by nitrogen doping. Numerous N-In bonds eliminate donorlike subgap states near the Fermi level, which improve stability during stress but degrade electron mobility. We developed tandem TFTs with an a-IZTO:N layer on top of an a-IZTO layer, in which mobility reaches 31.76 +/- 0.81 cm(2)/Vs and the reliability is improved. Especially, Delta V-th in NGBS is reduced by 80% for pristine a-IZTO devices. This simple but an effective method achieves fast and reliable operation in the a-IZTO TFTs.
Non-antireflective Scheme for Efficiency Enhancement of Cu(In,Ga)Se-2 Nanotip Array Solar Cells
(2013-08-01)
Liao, Yu-Kuang
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Wang, Yi-Chung
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Yen, Yu-Ting
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Chen, Chia-Hsiang
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Hsieh, Dan-Hua
We present systematic works in characterization of CIGS nanotip arrays (CIGS NTRs). CIGS NTRs are obtained by a one-step ion-milling process by a direct-sputtering process of CIGS thin films (CIGS TF) without a postselenization process. At the surface of CIGS NTRs, a region extending to 100 nm in depth with a lower copper concentration compared to that of CIGS TF has been discovered. After KCN washing, removal of secondary phases can be achieved and a layer with abundant copper vacancy (V-Cu) was left. Such compositional changes can be a benefit for a CIGS solar cell by promoting formation of Cd-occupied Cu sites (Cd-Cu) at the CdS/CIGS interface and creates a type-inversion layer to enhance interface passivation and carrier extraction. The raised V-Cu concentration and enhanced Cd diffusion in CIGS NTRs have been verified by energy dispersive spectrometry. Strengthened adhesion of Al:ZnO (AZO) thin film on CIGS NTRs capped with CdS has also been observed in SEM images and can explain the suppressed series resistance of the device with CIGS NTRs. Those improvements in electrical characteristics are the main factors for efficiency enhancement rather than antireflection.
Positive gate bias instability alleviated by self-passivation effect in amorphous InGaZnO thin-film transistors
(2015-12-02)
Li, GongTan
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Yang, Bo-Ru
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Liu, Chuan
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Lee, Chia-Yu
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Tseng, Chih-Yuan
The threshold voltage shift (Delta Vth) under positive gate bias stress (PGBS), generally found in amorphous InGaZnO thin-film transistors (a-IGZO TFTs), has usually been suppressed by external passivation layers. We report it can also be alleviated by the self-passivation effect of the active layer, where moderately increasing the active layer thickness (d(s)) reduces Delta Vth by 82% in SiOx-passivated a-IGZO TFTs. Our experiments in conjunction with simulations show that the instability of V-th comes from ambient factors at the back channel. Larger d(s) results in lower carrier concentrations at the back channel (N-back), fewer diffusive ions affecting the front channel, and much more stable operations under PGBS. The optimal thickness of an IGZO film simultaneously obtaining a small Delta V-th, near-zero Vth, and sharp sub-threshold swing is about 80-90 nm, thicker than those usually adopted. The self-passivation effect combined with the externally deposited passivation layer can improve the overall device reliability.
Subgap State Engineering Using Nitrogen Incorporation to Improve Reliability of Amorphous InGaZnO Thin-Film Transistors in Various Stressing Conditions
(2016-11)
Li, GongTan
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Zhan, Runze
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Yang, Bo-Ru
;
Liu, Chuan
;
Dong, ChengYuan
Instability of amorphous InGaZnO thin-film transistors (a-IGZO TFTs) remains an obstacle for commercialization. Here, we systematically discuss the effect of nitrogen incorporation on a-IGZO TFT stability and developed Ar/O-2/N-2 atmosphere to improve the stability under stressing in different conditions. Based on X-ray photoelectron spectrometer results, it is revealed that the positive gate bias stress (PGBS) stability is significantly improved due to microscopically passivated metal-oxygen bonds. Yet, the negative gate bias and light stress (NBLS) stability is seriously deteriorated with heavily nitrogen incorporation probably due to the bandgap narrowing effect. By optimizing a mixed O-2/N-2 atmosphere, the subgap states are finely tuned to afford optimal performance and stability. The developed IGZO TFTs exhibit mobility (12.67 cm(2)/Vs), small shift of threshold voltage under PGBS (reduced by 64% as compared with the pristine a-IGZO TFTs), and good negative gate bias stability and with NBLS stability as well.