Browsing by Author "Liu, TH"

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2-V-operation delta-doped power HEMT's for personal handy-phone systems
(1997-08-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Liu, TH
;
Wang, SP
A high-efficiency and high-power-density delta-doped AIGaAs/InGaAs HEMT with low adjacent channel leakage has been developed for the digital wireless personal handy-phone system (PHS). When qualified by 1.9-GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated PHS standard signals, the 2.0-V-operation HEMT with a 1-mm gate width demonstrated a power-added efficiency of 45.3% and an output power density of 105 mW/mm. This is the highest power density ever reported by the power transistors for the PHS. The state-of-the-art results for the PHS operating at 2.0 V were achieved by the delta-doped power HEMT for the first time.
2-V-operation delta-doped power HEMT's for personal handy-phone systems
(1997-08-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Liu, TH
;
Wang, SP
A high-efficiency and high-power-density delta-doped AIGaAs/InGaAs HEMT with low adjacent channel leakage has been developed for the digital wireless personal handy-phone system (PHS). When qualified by 1.9-GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated PHS standard signals, the 2.0-V-operation HEMT with a 1-mm gate width demonstrated a power-added efficiency of 45.3% and an output power density of 105 mW/mm. This is the highest power density ever reported by the power transistors for the PHS. The state-of-the-art results for the PHS operating at 2.0 V were achieved by the delta-doped power HEMT for the first time.
4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran doped red emitters in organic light-emitting devices
(2003-09-22)
Liu, TH
;
Iou, CY
;
Wen, SW
;
Chen, CH
;
應用化學系
We have studied the device optimization of red 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) dye doped Alq(3) emitters in organic light-emitting devices (OLED). By varying the hole injection materials, thickness of hole-transport layer and by evaporation with rubrene as co-dopant, efficiencies of 3.24 cd/A and near saturated CIE color coordinates of x = 0.643, y = 0.354 was achieved without needing additional doping of hole-trap with NPB. From experiments with film thickness variation, it is concluded that the improved electrofluorescent (EL) performance and color saturation are due to the synergistic effects of microcavity, device structural optimization as well as optimal doping of DCJTB with rubrene. We believe this luminance efficiency for red is by far one of the best ever reported for dye-doped electrofluorescent OLEDs. (C) 2003 Elsevier B.V. All rights reserved.
5 mm high-power-density dual-delta-doped power HEMT's for 3 V L-band applications
(1996-05-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Chen, TK
;
Liu, TH
A high-power-density dual-delta-doped AlGaAs/InGaAs/GaAs high electron mobility transistor (HEMT) for personal communication applications has been developed. A 5.0 mm gate-width device operating at a drain bias of 3.0 V gave an output power over 1 W, The 1 mu m gate-length HEMT exhibited a current density of 425 mA/mm at V-gs = 0.5 V, The maximum transconductance of the device was 270 mS/mm, The effective knee voltage was as low as 0.3 V, At the class AB operation, the HEMT demonstrated an output power density of 200 mW/mm, 64% power-added efficiency and 18.2 dB linear gain at 900 MHz, This is the highest power density of a dual-delta-doped AlGaAs/InGaAs/GaAs HEMT reported to date for low voltage (3 V) wireless applications.
5 mm high-power-density dual-delta-doped power HEMT's for 3 V L-band applications
(1996-05-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Chen, TK
;
Liu, TH
A high-power-density dual-delta-doped AlGaAs/InGaAs/GaAs high electron mobility transistor (HEMT) for personal communication applications has been developed. A 5.0 mm gate-width device operating at a drain bias of 3.0 V gave an output power over 1 W, The 1 mu m gate-length HEMT exhibited a current density of 425 mA/mm at V-gs = 0.5 V, The maximum transconductance of the device was 270 mS/mm, The effective knee voltage was as low as 0.3 V, At the class AB operation, the HEMT demonstrated an output power density of 200 mW/mm, 64% power-added efficiency and 18.2 dB linear gain at 900 MHz, This is the highest power density of a dual-delta-doped AlGaAs/InGaAs/GaAs HEMT reported to date for low voltage (3 V) wireless applications.
A new yellow fluorescent dopant for high-efficiency organic light-emitting devices
(2006-02-21)
Wu, YS
;
Liu, TH
;
Chen, HH
;
Chen, CH
;
應用化學系
We describe the design and synthesis of a sterically hindered yellow dopant, tetra(l-butyl)rubrene (TBRb) which, when doped in either 1,4-bis[N-(1-naphthyl)-N'-phenylamino]-biphenyl or aluminum tris(8-hydroxyquinoline) (Alq(3)) as emitter, shows nearly 25% increase in luminance efficiency over that of the state-of-the-art rubrene (Rb) device without significantly effecting its corresponding color. At 5% doping in Alq3 and 20 mA/cm(2) current drive condition, the electroluminescence efficiency of TBRb reaches 8.5 cd/A and 2.8 1m/W with a yellow color of Commission Internationale de l'Eclairage chromaticity coordinates (CIEx,y)=[0.52,0.48], which is among the best ever reported for yellow electrofluorescence in organic light-emitting devices. (c) 2005 Elsevier B.V. All rights reserved.
Development of highly stable organic electroluminescent devices with a doped co-host emitter system
(2005-03-01)
Liu, TH
;
Iou, CY
;
Chen, CH
;
光電工程學系
;
友訊交大聯合研發中心
Efficient red organic light-emitting devices based on the fluorescent dye "4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped in co-host emitter (CHE) systems of rubrene/tris(8-hydroxyquinolinato)aluminum (Alq(3)) [60/40] and of 9, 1 0-di(2-naphthyl)anthracene (ADN)/Alq(3) [60/40] which achieved a luminance efficiency of 4.2-5.5 cd/A at 20 mA/cm(2) with Commission Internationale d'Eclairage coordinates of [0.64,0.35]-[0.62,0.37]. At high rubrene or ADN concentration (>60%), this DCJTB doped CHE system has the advantage of alleviating the current-induced fluorescence quenching problem often encountered in red organic electroluminescence (EL) devices and greatly improves the EL efficiency over a wide range of drive current conditions. (C) 2004 Elsevier B.V. All rights reserved.
Doped blue emitters of 9,10-di(2-naphthyl)anthracene in organic electroluminescent devices
(2003-04-04)
Liu, TH
;
Shen, WJ
;
Yen, CK
;
Iou, CY
;
Chen, HH
Blue EL emission of 9,10-di(2-naphthyl)anthracene (ADN) based emitter in OLED is highly dependent upon its thickness and attenuated by the microcavity effect of the emitter. By carefully tuning the thickness of ADN and optimizing the doping concentration of TBP, one of the highest efficiencies reported for the anthracene based blue emitter at 6.6 cd/A with a CIE of x = 0.13; y = 0.21 is achieved.
Doped red organic electroluminescent devices based on a cohost emitter system
(2003-12-22)
Liu, TH
;
Iou, CY
;
Chen, CH
;
應用化學系
;
光電工程學系
We have developed an efficient red emitter in organic light-emitting diodes based on the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran doped in a cohost emitter system of 5,6,11,12-tetraphenylnathacene/tris(8-hydroxyquinolinato)aluminum which achieved an electroluminescence (EL) efficiency of 4.4 cd/A and 2.1 lm/W at 20 mA/cm(2) and 6.8 V, with a near saturated Commission Internationale d'Eclairage coordinates (x=0.65, y=0.35). This cohost emitter system has the advantage of alleviating the current-induced fluorescence quenching often encountered in red organic EL devices and greatly improves the EL efficiency over a wide range of drive current conditions. From accelerated degradation tests, a device half-life of about 33 800 h can be projected in this system at an initial device luminance of 100 cd/m(2). (C) 2003 American Institute of Physics.
Doped RGB organic electroluminescent devices based on a bipolar host material
(2003)
Wen, SW
;
Yen, CK
;
Liu, TH
;
Chen, CH
;
應用化學系
Development of RGB doped emitters based on the bipolar host of wide bandgap material, 9,10-bis(2-naphthyl)anthracene (ADN) is described. While the blue and green fluorescent dopants of TBP and C-545T achieved EL efficiencies of 5.1 and 11.2 cd/A, respectively in ADN, the red fluorescent DCJTB dopant needed to be doped in a co-hosted mixture of ADN. Alq(3) (60:40) in order to achieve a high efficiency of 4.8 cd/A with a near saturated CIEx,y = 0.64, 0.35 at 2% doping. Luminance efficiencies of all three RGB doped emitters in the bipolar ADN based host are not effected by increased drive current density, thus solving the current-induced fluorescence quenching problem often encountered in organic EL devices.
High-efficiency and low-distortion directly-ion-implanted GaAs power MESFET's for digital personal handy-phone applications
(1997-09-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Tai, MC
;
Liu, TH
We report a high-efficiency and low-distortion GaAs power MESFET using direct ion implantation technology for the digital wireless personal handy-phone system (PHS). When qualified by 1.9-GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated PBS standard signals, the 2.2-V-operation device with a gate width (W-g) of 2 mm exhibited a power-added efficiency (PAE) of 57.2% and an adjacent channel leakage power (P-adj) of -58 dBc at an output power of 21.3 dBm. The MESFET with the optimized direct ion implantation conditions and fabrication process achieved the highest PAE for PHS applications, The low-cost MMIC-oriented direct ion implantation technology has demonstrated the state-of-the-art results for new-generation PHS handsets for the first time.
High-performance pseudomorphic power HEMTs for low-voltage wireless communication applications
(1996)
Lai, YL
;
Chan, EY
;
Chang, CY
;
Liu, TH
;
Wang, SP
A high-performance pseudomorphic high electron mobility transistor (HEMT) with high output power density and high power-added efficiency for low-voltage wireless communication applications has been developed. This paper describes the de and microwave performance of the pseudomorphic AlGaAs/InGaAs HEMT developed. The 1 um gate-length HEMT exhibited a maximum drain current of 470 mA/mm at V-gs = +1.0 V. The maximum transconductance of the device was 280 mS/mm. At a drain bias of 3.0 V and a measurement frequency of 900 MHz, the 2mm-wide HEMT demonstrated an output power of 26.1 dBm ( a power density of 204 mW/mm) and a power-added efficiency of 65 % under the class AB condition while an output power of 26.7 dBm (234 mW/mm) and a power-added efficiency of 60 % were obtained under the class A condition. The developed pseudomorphic power HEMT developed achieves the highest output power density ever reported among the GaAs devices operating at 3.0 V.
High-power-density and high-efficiency atomic-planar-doped AlGaAs/InGaAs quantum-well power high-electron-mobility transistors for 2.4 V medium-power wireless communication applications
(1997-03-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Liu, TH
;
Wang, SP
A high-power-density and high-efficiency molecular-beam-epitaxy-grown atomic-planar-doped AlGaAs/InGaAs quantum-well power high-electron-mobility transistor (HEMT) was developed for low-voltage medium-power wireless communication applications. The HEMT exhibited a maximum drain current of 420 mA/mm and a maximum transconductance of 275 mS/mm. A two-dimensional electron gas with a high sheet charge density and a high electron mobility in the InGaAs quantum well contributed to the high current density and high transconductance of the HEMT and enhanced the device power performance at low operating voltage. An output power density of 177 mW/mm and a power-added efficiency of 61% were achieved by the 2 mm HEMT at a drain voltage of 2.4 V and a frequency of 900 MHz. At 2.1 V drain voltage and 2.4 GHz, frequency, the device demonstrated an output power of 24.4 dBm and a power-added efficiency of 57.4%. An adjacent channel leakage power of -55 dBc was attained for the 1.9-GHz pi/4-shifted quadrature phase shift keying modulation when the output power was 22.2 dBm and the drain voltage was 2.4 V.
Highly efficient yellow and white organic electroluminescent devices doped with 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene
(2004-11-08)
Liu, TH
;
Wu, YS
;
Lee, MT
;
Chen, HH
;
Liao, CH
We describe the applications of a sterically-hindered yellow dopant, 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (TBRb) which, when compared to 5,6,11,12-tetraphenylnaphthacene (Rb) in either tris(8-hydroxyquinolinato)aluminum or 1,4-bis[N-(1-naphthyl)-N-'-phenylamino]-4,4(') diamine (NPB) as host emitter, shows a 50%-34% increase in luminance efficiency over that of Rb device without significantly affecting its color. In addition, we have incorporated the TBRb doped yellow NPB emitter into the two-element white organic light-emitting diodes based on p-bis(p-N,N-di-phenyl-aminostyryl)benzene doped 2-methyl-9,10-di(2-naphthyl) anthracene sky-blue emitter which improved the luminance efficiency by 44% over that of Rb to 12.8 cd/A and 4.3 lm/W at 20 mA/cm(2) with CIEx,y=[0.31,0.38]. (C) 2004 American Institute of Physics.
Phosphorescence of red Os(fptz)(2)(PPh2Me)(2) doped organic light-emitting devices with n and p hosts
(2006-02-06)
Liu, TH
;
Hsu, SF
;
Ho, MH
;
Liao, CH
;
Wu, YS
We have applied a stericly-hindered red phosphorescent dopant Os(fptz)(2)(PPh2Me)(2) [fptz=3-trifluoromethyl-5-(2-pyridyl)-1,2,4-triazole, PPh2Me=phosphine ligand] in p-type 4,4(')-N,N-'-dicarbazole-biphenyl or n-type bis(2-methyl-8-quinolinolato)(p-phenylphenolato) aluminum host and found that the latter produced higher luminance efficiency at lower doping concentration. We present a model to rationalize this phenomenon in which the n-type host impedes hole transport, which leads to narrower recombination zone near the hole transport layer/emission layer interface than the p-type host, hence, more effective recombination.
Spirobifluorene-linked bisanthracene: An efficient blue emitter with pronounced thermal stability
(2004-03-09)
Shen, WJ
;
Dodda, R
;
Wu, CC
;
Wu, FI
;
Liu, TH
Spiro-FPA, a novel blue emitter, in which two identical anthracene luminophores are linked orthogonally around a spirobifluorene core, has been synthesized and characterized. The introduction of a spiro linkage into the structure of spiro-FPA leads to a reduction in crystallization tendency and an increase in glass transition temperature relative to the monomeric units. In addition, the tetrahedral nature of the carbon atom at the spiro center preserves the optical and electrochemical characteristics of the pristine anthracene units. As demonstrated by AFM measurements, high-quality amorphous films of spiro-FPA with good morphological stability can be prepared by vapor deposition. Organic EL devices constructed using a 1.0-wt % TBP-doped spiro-FPA emitting layer produce bright blue emissions with a high luminescence efficiency of 4.9 cd/A (2.07 lm/W).