Browsing by Author "Tsai, CM"

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10-Gb/s modulator drivers with local feedback networks
(2006-05-01)
Li, DU
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Tsai, CM
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel intrinsic collector-base capacitance (C(CB)) feedback network (ICBCFN) was incorporated into the conventional cascode and series-connected voltage balancing (SCVB) circuit configurations to implement 10-Gb/s modulator drivers. The drivers fabricated in 0.35-mu m SiGe BiCMOS process could generate 9 V(PP) differential output swings with rise/fall time of less than 29 ps. Also, the ICBCFN was modified as an intrinsic drain-gate capacitance feedback network (IDGCFN) to implement drivers with differential output swing of 8 V(PP) in 0.18-mu m CMOS process. The power consumption is as low as 0.6 W. The present work shows that the driving capability is greater than that of the currently reported Silicon-based drivers.
980 nm InGaAs/AlGaAs quantum well lasers with extremely low beam divergence
(1996)
Yen, ST
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Lin, G
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Liu, DC
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Tsai, CM
;
Lee, CP
A 10-Gb/s laser diode driver in 0.35 mu m BiCMOS technology
(2005)
Wang, TY
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Chen, WZ
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Tsai, CM
;
Huang, LR
;
Li, DU
This paper describes the design of a 10Gb/s laser diode (LD) driver in a 0.35 mu m SiGe BiCMOS technology. The LD driver delivers a biased current up to 60 mA, and a modulation current ranges from 40 mA to 100 mA. High speed operation as well as high current driving capability are achieved by means of push-pull current switching scheme. In addition, negative Miller capacitor compensation technique is adopted to enhance the signal bandwidth. The output swing of the predriver is dynamically adjustable to compromise between operating speed and overshoot. Both the modulation and biased currents are derived from a bandgap reference source. The measured rise/fall time is 47ps, and timing jitter is 22.2ps(p-p). The eye diagrams meet the specifications defined by SONET OC-192 and 10G Ethernet eye mask. Operating under 3.3V/7V supply, the total power consumption is 1.38W. Chip size is 1430 x 940 mu m(2).
Binarization of color document images via luminance and saturation color features
(2002-04-01)
Tsai, CM
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Lee, HJ
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資訊工程學系
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Department of Computer Science
This paper presents a novel binarization algorithm for color document images. Conventional thresholding methods do not produce satisfactory binarization results for documents with close or mixed foreground colors and background colors. Initially, statistical image features are extracted from the luminance distribution. Then, a decision-tree based binarization method is proposed, which selects various color features to binarize color document images. First, if the document image colors are concentrated within a limited range, saturation is employed. Second, if the image foreground colors are significant, luminance is adopted. Third, if the image background colors are concentrated within a limited range, luminance is also applied. Fourth, if the total number of pixels with low luminance (less than 60) is limited, saturation is applied; else both luminance and saturation are employed. Our experiments include 519 color images, most of which are uniform invoice and name-card document images. The proposed binarization method generates better results than other available methods in shape and connected-component measurements. Also, the binarization method obtains higher recognition accuracy in a commercial OCR system than other comparable methods.
Compositional disordering of InGaAs/GaAs heterostructures by low-temperature-grown GaAs layers
(1996-01-15)
Tsang, JS
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Lee, CP
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Lee, SH
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Tsai, KL
;
Tsai, CM
Compositional disordering of InGaAs/GaAs superlattices using a low-temperature-grown GaAs cap layer (LT-GaAs) by molecular beam epitaxy has been studied. The disordering of the superlattice was verified by photoluminescence and double-crystal x-ray rocking curve measurements. The Ga-vacancy-enhanced interdiffusion due to the presence of LT-GaAs was found to be the disordering mechanism. Diffusion equations and the Schrodinger's equation were solved numerically to obtain the composition profile and the transition energies in the disordered quantum well, respectively. The simulated energy shifts for samples under different annealing conditions agreed very well with the experimental results. The calculated effective diffusivity for the In-Ga interdiffusion has an activation energy of 1.63 eV, which is smaller than the activation energy 1.93 eV, for intrinsic interdiffusion. The diffusivity for the enhanced In-Ga interdiffusion due to the presence of LT-GaAs is about two orders of magnitude larger than the intrinsic In-Ga diffusivity. (C) 1996 American Institute of Physics.
High-performance two-wavelength asymmetric Fabry-Perot modulator with a decoupled cavity design
(1998-03-01)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have demonstrated a high-performance two-wavelength asymmetric Fabry-Perot modulator (AFPM) by using a novel decoupled cavity design, In this new design, the middle mirror supplies a back-mirror reflectivity for the short-wavelength modulator and, at the same time, a front-mirror reflectivity for the long-wavelength modulator. The front mirror is designed to be transparent at the long wavelength and reflective at the short wavelength to eliminate the interference between the two modulators, With this decoupled cavity design, we greatly simplified the matching requirement for the two cavities and obtain much more flexibility in the device design. Experimentally, we have demonstrated a two-wavelength modulator operated at 860 and 890 mn with operating voltages of 3.4 and 6.2 V and reflectivity changes of 62% and 44%, respectively.
Low-resistance vertical conduction across epitaxially lifted-off n-GaAs film and Pd/Ge/Pd coated Si substrate
(1998-03-01)
Fan, JC
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Tsai, CM
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Chen, KY
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Wang, SY
;
Lin, G
Low-resistance ohmic conduction across an epitaxially lifted-off(ELO) thin n-GaAs film and a Si substrate was obtained by attaching the ELO film on the Si substrate coated with a Pd/Ge/Pd multilayer. Good bonding and ohmic contacts to both GaAs and Si were achieved at the same time after annealing. The interface compound formation was studied by secondary ion mass spectroscopy and x-ray diffraction analyses. This ELO technology was used to fabricate an ELO stripe geometry diode laser on Si with the back-side contact on Si substrate. Good laser performance with comparable characteristics as conventional laser diodes on GaAs substrates was obtained.
Normally on reflection-type two-wavelength quantum-well modulator with balanced cavity design
(1997-07-01)
Tsai, CM
;
Lee, CP
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have demonstrated a reflection-type two-wavelength modulator with a novel balanced cavity design, Simultaneous operations at wavelengths of around 860 and 896 nm have been achieved. By using such a new cavity design similar operating voltages have been obtained for both wavelengths. Under separate biasing voltages of 14.5 and 11 V on each quantum-well absorbing region, the maximum reflectivity changes were around 50%.
Optical and structural properties of epitaxially lifted-off GaAs films
(1998-01-01)
Fan, JC
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Lee, CP
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Tsai, CM
;
Wang, SY
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Tsang, JS
The influence of the layer thickness on the optical and structural properties of the epitaxially lifted-off (ELO) thin films has been studied. The ELO films bonded to Si, InP, and GaAs substrates have also been compared. The structure was characterized by high-resolution double-crystal x-ray diffraction and the optical properties were measured by the temperature-dependent photoluminescence spectroscopy. A biaxial compressive strain was observed for the samples bonded to Si with a buffer layer thinner than 1000 nm. Due to different thermal expansion coefficient between the grafted thin film and the host substrate, the emission spectra of the quantum wells of the lifted-off thin films are redshifted compared to the as-grown sample. The amount of the redshift is larger for thinner films. (C) 1998 American Institute of Physics.
Reflection-type normally-on two-wavelength modulator
(1997-03-27)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The authors demonstrate a novel reflection-type normally-on two-wavelength modulator by combining two quantum-well structures with different operating wavelengths in a coupled cavity structure. Reflection spectra show simultaneous modulations at wavelengths of 856 and 886 nm in the device consisting of GaAs/A1GaAs and InGaAs/A1GaAs quantum wells for each wavelength. Under separate applied voltages, maximum reflectivity changes of 70 and 54% were obtained for the two wavelengths. To the best of the authors' knowledge, this is the First two-wavelength reflection modulator ever reported.
Reflection-type normally-on two-wavelength modulator
(1997-03-27)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The authors demonstrate a novel reflection-type normally-on two-wavelength modulator by combining two quantum-well structures with different operating wavelengths in a coupled cavity structure. Reflection spectra show simultaneous modulations at wavelengths of 856 and 886 nm in the device consisting of GaAs/A1GaAs and InGaAs/A1GaAs quantum wells for each wavelength. Under separate applied voltages, maximum reflectivity changes of 70 and 54% were obtained for the two wavelengths. To the best of the authors' knowledge, this is the First two-wavelength reflection modulator ever reported.
Reflection-type two-wavelength quantum well modulators
(1997-07-01)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A systematic way has been developed for cavity design of reflection-type two-wavelength modulators based on coupled cavity structures. By inserting a properly designed additional reflector between the two quantum well absorbing layers with different designed operating wavelengths, two modulator structures can be combined with different operating wavelengths in one device and they can be made to operate almost independently. In this paper, three types of two-wavelength cavity designs including the simple cavity, the balanced cavity, and the decoupled cavity, are described. Their merits and drawbacks in overall modulation performance are compared. The three designs have also been realized experimentally. All of the three devices show clearly independent two-wavelength operation and the measured characteristics agree with the theoretical predictions.
Star-like fluorene based polyamines: non-conjugated building blocks for light-harvesting materials
(2006-04-10)
Thomas, KRJ
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Lin, JT
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Tsai, CM
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Lin, HC
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材料科學與工程學系
We report herein a series of novel tetramines (2-6) built using the fluorene core. The design features a diamine conjugated by a fluorene core and two non-conjugated triarylamines dangling through the bridge methine moiety. These polyamines are amorphous in nature and display moderate emission properties that are either dependent on the nature of the arylamine segments or reminescent of the fluorene backbone. The phenyl, naphthyl, fluorenyl and carbazolyl amine based materials are blue emissive while the pyrenylamine based compound emits yellow-green color. We demonstrate a possibility of using blue-emitting fluorene derivatives (2 and 4) blended with poly(N-vinylcarbazole) (PVK) to fabricate organic light emitting diodes (OLEDs). Emissions in the EL devices purely originated from the fluorene derivatives alone (blue) are contaminated with those of complex species (electromer/electroplex) formed by intermolecular interactions. (c) 2006 Elsevier Ltd. All rights reserved.
Synthesis and characterization of alternating fluorene-based copolymers containing diaryl- and non-substituted bithiophene units
(2005-11-14)
Lin, HC
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Sung, HH
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Tsai, CM
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Li, KC
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材料科學與工程學系
A series of soluble alternating fluorene-based copolymers containing diaryl- and non-substituted bithiophene units are synthesized by palladium-catalyzed Suzuki coupling reaction. All polymers demonstrate green colors of photoluminescence (PL) in chloroform, good thermal stability (with, decomposition temperatures above 436 degrees C), and high glass transition temperatures (in the range of 120-144 degrees C). Owing to the large steric hindrance of diaryl substituents on bithiophenes in the polymers (P2-P4), the aggregation of solids is reduced as well as the solubility is improved, so the performance of their PLED devices are superior to that of the non-substituted polymer (PI). Compared with P1, the introduction of substitutents at 3,3'-position of bithiophene in P2-P4 has significant effects on the photophysical properties of resulting polymers in solution and solid states. Though the PL quantum yield of P1 is much higher than those of diaryl-substituted polymers (P2-P4), the PLED device of P1 has the worst electroluminescence (EL) properties due to the poor solubility of P1. Consequently, among these polymers, the device made of P3 as an emitter has the highest luminance of 2590 cd/m(2) at 9.5 V. For optimum device performance, a device of P3 blended with PVK can be further enhanced to a brighter luminance of 4284 cd/m(2) at 18 V. (c) 2005 Elsevier Ltd. All rights reserved.
Synthesis and characterization of light-emitting H-bonded complexes and polymers containing bis(pyridyl) emitting acceptors
(2006-01-24)
Lin, HC
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Tsai, CM
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Huang, GH
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Tao, YT
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材料科學與工程學系
A series of bis(pyridyl) acceptor emitters are synthesized and the LC and photophysical (PL and EL) properties of their supramolecular structures, including H-bonded polymer networks and trimers, are explored. Unique mesomorphic properties may be introduced into these H-bonded complexes and polymers containing nonmesogenic acceptor emitters. In addition, the emission properties of bis(pyridyl) acceptor emitters can be adjusted by their surrounding nonphotoluminescent proton donors. Compared with pure bis(pyridyl) acceptor emitters, red-shifts of PL emission wavelengths were observed in most of the H-bonded complexes and polymers. Because of the higher acidity value of m-PC(10)BA (16) and its stronger H-bonded effect in H-bonded polymer complexes, the largest red-shift of 93 nm in lambda(max) value of PL has occurred in the fully H-bonded polymer network p-PBBBP-OC8 (8)/m-PC(10)BA (16) in contrast to pure emitter p-PBBBP-OC8 (8). A very narrow full width at half-maximum (fwhm) value (38 nm) of EL spectra can be obtained in the device of H-bonded complexes blended with PVK, and a higher brightness of EL is produced at an appropriate annealing temperature.
Synthesis and characterization of light-emitting oligo(p-phenylene-vinylene)s and polymeric derivatives containing three- and five-conjugated phenylene rings
(2006-01-15)
Lin, HC
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Tsai, CM
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Huang, GH
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Lin, JM
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材料科學與工程學系
Several series of light-emitting oligo(p-phenylene-vinylene)s (BIII and BV series containing three- and five-conjugated phenylene rings) with various side groups and end groups attached to the cores were synthesized and characterized. The analogous PBV polymers, derived from the BV series, were also synthesized and investigated. Blue and greenish light emissions were observed in the photoluminescence (PL) and electroluminescence (EL) spectra of the blend and pure films with these pi-conjugated structures. In contrast to the three-conjugated ring oligomers, the five-conjugated ring derivatives (oligomers and polymers) had larger maximum emission wavelength values of PL and EL emissions. Mesomorphism was introduced into the BV series by the replacement of three-conjugated rings (BIII series) with five-conjugated phenyl cores (BV series). The liquid-crystalline properties of the BV series with end groups (on both end rings) were better than those of analogous BV-OC8 without end groups. Polarized PL emissions were obtained by the alignment of liquid-crystalline phase in rubbing cells. Upon heating, different PL emission wavelengths and intensities were observed in various phases. Not only the solubility and thermal properties but also the PL and EL properties could be effectively adjusted by the attachment of flexible alkoxy groups either on the central rings or on both end rings of the conjugated cores. (c) 2005 Wiley Periodicals, Inc.
Synthesis and characterization of light-emitting oligo(p-phenylene-vinylene)s and polymeric derivatives containing three- and five-conjugated phenylene rings. II. Electro-optical properties and optimization of PLED performance
(2006-05-01)
Lin, HC
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Tsai, CM
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Tao, YT
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材料科學與工程學系
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Department of Materials Science and Engineering
A series of multilayer polymeric light-emitting diodes (PLEDs) containing an electron-transporting layer (ETL), that is tris(8-quinolinolato)-aluminum(III) (Alq) and 2,2',2"-(1,3,5-phenylene)-tris[1-phenyl-1H-benzimidazole] (TPBI), were fabricated by doping fluorescent oligo(p-phenylene-vinylene)s (BIII and BV) and polymer derivatives (PBV) into poly(N-vinyl carbazole) (PVK). These PLEDs can be optimized by the design of multilayer device configurations (brightness increased 8-15 times by addition of ETL) and possess greenish electroluminescent (EL) spectra peaked about 500-540 nm. A remarkably high brightness of 56,935 cd/m(2) with a power efficiency of 3.25 lm/W was obtained in the device of PVK:BVOC8-OC8 (100:20)/Alq (60 nm/60 nm). It suggests that the emission mechanism (including the conjugated and excimer emissions of BVOC8-OC8 emitters) originates from both of BVOC8-OC8 and ETL (Alq and TPBI) by varying the concentration of chromophores and adjusting the thickness of ETL. The concentration effect of the emitters in PVK (i.e. PVK:BVOC8-OC8 = 100:5, 100:20, and 100:100 wt %) and the influence of the ETL (including its thickness) on the EL characteristics are also reported. (c) 2006 Wiley Periodicals, Inc.
Synthesis and characterization of rod-coil polymers based on poly(ethylene oxide)s sand novel luminescent aromatic cores
(2006-05-30)
Lin, HC
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Lee, KW
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Tsai, CM
;
Wei, KH
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材料科學與工程學系
A novel conjugated aromatic core containing direct-coupled fluorene, thiophene, and biphenyl groups via Suzuki coupling reaction was synthesized. The asymmetrical molecules contain two kinds of poly( ethylene oxide)s (PEO, M-n = 750 and 2000, n = 17 and 44) on one side of the rigid cores. Asymmetrical FOC8PEO17 and FOC16PEO17 contain flexible PEO chains (n = 17) displaying the smectic phases. However, FOC8PEO44 and FOC16PEO44 consisting of flexible PEO chains ( n = 44) exhibit two kinds of columnar phases, Col(h) and Col(r). Besides, alkoxy groups with different lengths (- OC(8)H(17)and - OC16H33) on both sides of the rigid cores were used as another flexible chain to form symmetrical molecules. Symmetrical FOC8 and FOC16 exhibit the nematic and smectic mesophases, respectively. Optical textures (POM) and XRD patterns have confirmed the structure of the mesophases and the molecular arrangements. The photophysical characteristics of all luminescent compounds were studied by photoluminescence and UV-vis absorption. In addition, a series of double-layered PLED devices with the configuration of PVK: emitters( 100: 8 by weight)/TPBI/MgAg/Ag were fabricated and investigated.
The effect of barrier structure on the performance of double barrier quantum well infra-red photodetectors
(1996-02-01)
Tsai, KL
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Lee, CP
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Chen, PC
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Tsang, JS
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Tsai, CM
The effects of the inner and outer barriers on the performance of mid-wavelength (3-5 mu m) GaAs/AlGaAs double barrier quantum well infra-red photodetectors (DBQWIPs) have been studied. It was found that the peak response wavelength had a significant red shift when the thickness of the AlAs inner barriers was below 10 Angstrom. This is attributed to the lowering of the upper state energy in the quantum wells. The responsivity of DBQWIPs decreases with the inner barrier thickness. This is because the optical gain decreases faster than the increasing rate of the quantum efficiency when the inner barrier thickness increases. The responsivities for devices with different Al compositions (0.35 and 0.24) in the outer barriers are in the same range, but the dark currents for devices with Al(0.35)G(0.65)As outer barriers are much lower than those with Al0.24Ga0.76As outer barriers. Nearly two orders of magnitude improvement in detectivity was observed when the Al composition in the outer barriers was changed from 0.24 to 0.35. A high detectivity of 1 x 10(11) cm Hz(1/2) W-1 at 77 K was obtained for a device with 12 Angstrom AlAs inner barriers and 300 Angstrom Al0.35Ga0.65As outer barriers.
Thermal annealing of Pd/InAlAs Schottky contacts for transistor buried-gate technologies
(1998-01-01)
Chuang, HF
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Lee, CP
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Tsai, CM
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Liu, DC
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Tsang, JS
We studied the thermal reaction of Pd/In0.52Al0.48As contacts using capacitance-voltage (C-V), current-voltage, Auger electron spectroscopy, and x-ray diffraction analyses and compared the results to those for Pd/Al0.25Ga0.75As and Pd/In0.53Ga0.47As contacts. The thickness of InAlAs consumed by the reaction during annealing was calculated directly from the measured C-V profiles. Pd starts to react with InAlAs at a temperature of 100 degrees C, lower than it does with AlGaAs. For thermally annealed Pd/InAlAs and Pd/AlGaAs, both compositional and structural changes were found at the Pd/semiconductor interface. However, in heat-treated Pd/InGaAs samples, compositional changes but no structural changes were observed. (C) 1998 American Institute of Physics.