Browsing by Author "Lee, Ching-Ting"

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460-nm InGaN-Based LEDs Grown on Fully Inclined Hemisphere-Shape-Patterned Sapphire Substrate With Submicrometer Spacing
(2009-10-01)
Chang, Chia-Ta
;
Hsiao, Shih-Kuang
;
Chang, Edward Yi
;
Hsiao, Yu-Lin
;
Huang, Jui-Chien
This letter investigates 460-nm InGaN-based light-emitting diodes (LEDs) grown on a hemisphere-shape-patterned sapphire substrate (HPSS) with submicrometer spacing. The full-width at half-maximum of the (102) plane rocking curves for GaN layer grown on a conventional sapphire substrate (CSS) and HPSS are 480 and 262 arcsec, respectively. Such improvement is due to the reduction of the pure edge threading dislocations. At the forward current of 20 mA, the light output power of the LEDs grown on CSS and HPSS were 4.05 and 5.86 mW, respectively. This improvement of 44% light-output power can be attributed to the improved quality of the material and the increase of the light extraction by the fully inclined facets of the HPSS.
A Cu-based alloyed ohmic contact system on n-type GaAs
(2007-12-03)
Chen, Ke-Shian
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Chang, Edward Yi
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Lin, Chia-Ching
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Lee, Cheng-Shih
;
Huang, Wei-Ching
An alloyed Pd/Ge/Cu Ohmic contact to n-type GaAs is reported for the first time. The Pd/Ge/Cu Ohmic contact exhibited a very low specific contact resistance of 5.73x10(-7) Omega cm(2) at a low annealing temperature of 250 degrees C. This result is comparable to the reported Pd/Ge and Au/Ge/Ni Ohmic contact systems to n-type GaAs with doping concentrations about 1x10(18) cm(-3). The Ohmic contact formation mechanisms and microstructure evolution were investigated using secondary ion mass spectrometry, x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometer. The Ohmic contact behavior was related to the formation of Cu(3)Ge and PdGa(x)As(y) compounds after annealing. (c) 2007 American Institute of Physics.
Changes of Electrical Characteristics for AlGaN/GaN HEMTs Under Uniaxial Tensile Strain
(2009-03-01)
Chang, Chia-Ta
;
Hsiao, Shih-Kuang
;
Chang, Edward Yi
;
Lu, Chung-Yu
;
Huang, Jui-Chien
This letter investigates the characteristics of unpassivated AlGaN/GaN high-electron mobility transistors (HEMTs) under uniaxial tensile strain. Mechanical stress can produce additional charges that change the HEMT channel current. is phenomenon is dependent upon gate orientation and may be the result of the piezoelectric effect and changes in electron mobility due to the applied uniaxial stress. In addition, results show that tensile strain reduces the transient current, which is, likely due to the additional donorlike surface states created through the piezoelectric effect.
Copper-airbridged low-noise GaAs PHEMT with Ti/WNx/Ti diffusion barrier for high-frequency applications
(2006-08-01)
Lee, Cheng-Shih
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Lien, Yi-Chung
;
Chang, Edward Yi
;
Chang, Huang-Choung
;
Chen, Szu-Houng
A GaAs pseudomorphic HEMT (PHEMT) with Cu-metallized interconnects was successfully developed. Sputtered WNx was used as the diffusion barrier and Ti was used as the adhesion layer to improve the adhesion between WNx/Cu interface in the thin-metal structure. After copper metallization, the PHEMTs were passivated with silicon nitride to avoid copper oxidation. The Cu-airbridged PHEMT showed the saturation I-DS was 250 mA/mm and the g(m) was 456 mS/mm. The Ti adhesion layer plays a significant role on the g(m) and V-p uniformity of the Cu-metallized PHEMTs. The GaAs PHEMTs with Ti/WNx/Ti/Cu multilayer have better noise figure and associated gain than those of the devices without the Ti adhesion layer. The fabricated Cu-metallized GaAs PHEMT with Ti/WNx/Ti/Cu multilayer has a noise figure of 0.76 dB and an associated gain of 8.8 dB at 16 GHz. The cutoff frequency (f(T)) is 70 GHz when biased at V-DS = 1.5 V. These results show that the Ti/WNx/Ti multilayer can serve as a good diffusion barrier for Cu metallization process of airbridge interconnects on GaAs low-noise PHEMTs.
Crystal structure control of Au-free InAs and InAs/GaSb heterostucture nanowires grown on Si (111) by metal-organic chemical vapor deposition
(2019-01-01)
Kakkerla, Ramesh Kumar
;
Anandan, Deepak
;
Singh, Sankalp Kumar
;
Yu, Hung Wei
;
Lee, Ching-Ting
In this letter, the growth of gold-free GaSb on various InAs nanowire (NW) crystal structures using metal-organic chemical vapor deposition is demonstrated. The GaSb was grown radially and axially on wurtzite (WZ), zinc-blend (ZB) and polytype (mixture of WZ and ZB) InAs NWs. The effect of the various InAs crystal structures on GaSb was studied. This study demonstrates the control of the crystal growth of InAs and InAs/GaSb heterostructure NWs through the optimization of growth parameters and crystal transfer from core to shell, such techniques are necessary for the growth of NWs for future nanoelectronic device applications, such as TFET. (C) 2018 The Japan Society of Applied Physics
Design and Fabrication of 0/1-Level RF-Via Interconnect for RF-MEMS Packaging Applications
(2010-02-01)
Hsu, Li-Han
;
Wu, Wei-Cheng
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Chang, Edward Yi
;
Zirath, Herbert
;
Wu, Yun-Chi
This paper presents the parametric study of RF-via (0-level) and flip-chip bump (1-level) transitions for applications of packaging coplanar RF-MEMS devices. The key parameters were found to be the bumps' and vias' positions and the overlap of the metal pads, which should be carefully considered in the entire two levels of packages. The length of the backside transmission line, determining the MEMS substrate area, showed minor influence on the interconnect performance. With the experimental results, the design rules have been developed and established. The optimized interconnect structure for the two levels of packages demonstrates the return loss beyond 15 dB and the insertion loss within 0.6 dB from dc to 60 GHz.
Electrical Characteristics of Al2O3/InSb MOSCAPs and the Effect of Postdeposition Annealing Temperatures
(2013-05-01)
Hai Dang Trinh
;
Lin, Yueh Chin
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Chang, Edward Yi
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Lee, Ching-Ting
;
Wang, Shin-Yuan
The characteristics of Al2O3/InSb MOSCAPs processed with different postdeposition annealing (PDA) temperatures are investigated. X-ray photoelectron spectroscopy analysis shows a significant reduction of InSb-oxides after HCl plus trimethyl aluminum treatment and oxide deposition. Multifrequency capacitance-voltage (C-V) characteristics exhibit low-frequency and asymmetrical C-V behaviors, in which capacitance in the InSb conduction band side is lower than in the valence band side. The electrical properties of the MOSCAPs are sensitive to PDA temperature and degraded significantly at PDA temperature > 300 degrees C. This degradation is closely related to the diffusion of In, Sb into Al2O3 as indicated by transmission electron microscopy analyses.
Enhanced light harvesting of nitride-based nanopillars covered with ZnO using indium-tin oxide nanowhiskers
(2014-04-01)
Hsu, Lung-Hsing
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Lin, Chien-Chung
;
Lee, Hsin-Ying
;
Huang, Jhih-Kai
;
Han, Hau-Vei
Nitride-based nanopillars were successfully fabricated by nanoimprint lithography. A nanowhisker of indium-tin oxide (ITO) deposited by on oblique evaporation method was investigated in nitride-based nanopillars and thin ZnO layers grown by atomic layer deposition (ALD). From the results of field-emission scanning electron microscopy (SEM) measurement, it was found that ITO whiskers grew on nitride-based nanopillars covered with ZnO. Moreover, from the results of UV-visible spectrophotometry and bidirectional reflectance distribution function (BRDF) measurements, it was found that this hybrid structure of ITO nanowhiskers above a ZnO medium enhanced the broadband and angle-independent antireflection in the range between 380 and 600nm. We used the hybrid design of the ITO/ZnO structure to achieve the lowest reflectance value between 3.8 and 10.9% in a quantum well absorption range. (C) 2014 The Japan Society of Applied Physics
Fabrication and characterization of n-In0.4Ga0.6N/p-Si solar cell
(2012-07-01)
Tran, Binh-Tinh
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Chang, Edward-Yi
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Trinh, Hai-Dang
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Lee, Ching-Ting
;
Sahoo, Kartika Chandra
Electro-optic characteristics of a fabricated n-In0.4Ga0.6N/p-Si hetero-structure solar cell on Si substrate with Al and ITO (or Ti/Al/Ni/Au) materials for p and n-type contacts were investigated in this letter. The solar cell devices with ITO as n-type contacts were also compared to the solar cell using Ti/Al/Ni/Au as n-type contact in this study. High short-circuit current density observed for solar cell with ITO as n-type contacts due to the increased amount of light reaching the solar cell. The device with ITO contact exhibited an open-circuit voltage (V-oc) of 1.52 V and a short-circuit current density (J(sc)) of 8.68 mA/cm(2) with 54% fill factor. The conversion and external quantum efficiency (EQE) of the solar cell were 7.12 and 20.8%, respectively. Besides, a relationship between V-oc and In content in the InxGa1-xN alloys for this type of solar cell was also derived. (C) 2012 Elsevier B.V. All rights reserved.
Fabrication of 0.15-mu m Gamma-shaped gate In0.52Al0.48As/In0.6Ga0.4As metamorphic HEMTs using DUV lithography and tilt dry-etching technique
(2007-02-01)
Lien, Yi-Chung
;
Chen, Szu-Hung
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Chang, Edward Yi
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Lee, Ching-Ting
;
Chu, Li-Hsin
An In0.52Al0.48As/In0.6Ga0.4As metamorphic high-electron mobility transistor (MHEMT) with 0.15-mu m Gamma-shaped gate using deep ultraviolet lithography and tilt dry-etching technique is demonstrated. The developed submicrometer gate technology is simple and of low cost as compared to the conventional E-beam lithography or other hybrid techniques. The gate length is controllable by adjusting the tilt angle during the dry-et ching process. The fabricated 0.15-mu m In0.52Al0.48As/In0.6Ga0.4As MHEMT using this novel technique shows a saturated drain-source current of 680 mA/mm and a transconductance of 728 mS/mm. The f(T) and f(max) of the MHEMT are 130 and 180 GHz, respectively. The developed technique is a promising low-cost alternative to the conventional submicrometer E-beam gate technology used for the fabrication for GaAs MHEMTs and monolithic microwave integrated circuits.
Growth of GaN film on 150 mm Si (111) using multilayer AlN/AlGaN buffer by metal-organic vapor phase epitaxy method
(2007-11-26)
Lin, Kung-Liang
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Chang, Edward-Yi
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Hsiao, Yu-Lin
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Huang, Wei-Ching
;
Li, Tingkai
High quality GaN film was successfully grown on 150 mm Si (111) substrate by metal-organic vapor phase epitaxy method using AlN multilayer combined with graded AlGaN layer as buffer. The buffer layer structure, film quality, and film thickness are critical for the growth of the crack-free GaN film on Si (111) substrate. Using multilayer AlN films grown at different temperatures combined with graded Al(1-x)Ga(x)N film as the buffer, the tensile stress on the buffer layer was reduced and the compressive stress on the GaN film was increased. As a result, high quality 0.5 mu m crack-free GaN epitaxial layer was successfully grown on 6 in. Si substrate. (C) 2007 American Institute of Physics.
Growth of High-Quality In(0.4)Ga(0.6)N Film on Si Substrate by Metal Organic Chemical Vapor Deposition
(2011-11-01)
Binh-Tinh Tran
;
Chang, Edward-Yi
;
Lin, Kung-Liang
;
Wong, Yuen-Yee
;
Sahoo, Kartika Chandra
High-quality In(0.4)Ga(0.6)N film grown on GaN/AlN/Si(111) templates was obtained by metal organic chemical vapor deposition (MOCVD) with negligible phase separation. A template of high-quality GaN grown on a Si(111) substrate using AlN buffer layers was used for subsequent In(0.4)Ga(0.6)N growth. The GaN layer was 0.6 mu m thick with rocking-curve full width at half maximum (FWHM) for a GaN(002) peak better than 430 arcsec. The In(0.4)Ga(0.6)N film grown was 0.3 mu m thick with a dislocation density of 6 x 10(7) cm(-2) and X-ray (omega-2 theta) FWHM better than 130 arcsec. (C) 2011 The Japan Society of Applied Physics
Growth of High-Quality In0.4Ga0.6N Film on Si Substrate by Metal Organic Chemical Vapor Deposition
(2011-11-01)
Binh-Tinh Tran
;
Chang, Edward-Yi
;
Lin, Kung-Liang
;
Wong, Yuen-Yee
;
Sahoo, Kartika Chandra
High-quality In0.4Ga0.6N film grown on GaN/AlN/Si(111) templates was obtained by metal organic chemical vapor deposition (MOCVD) with negligible phase separation. A template of high-quality GaN grown on a Si(111) substrate using AlN buffer layers was used for subsequent In0.4Ga0.6N growth. The GaN layer was 0.6 mu m thick with rocking-curve full width at half maximum (FWHM) for a GaN(002) peak better than 430 arcsec. The In0.4Ga0.6N film grown was 0.3 mu m thick with a dislocation density of 6 x 10(7) cm(-2) and X-ray (omega-2 theta) FWHM better than 130 arcsec. (C) 2011 The Japan Society of Applied Physics
Improved Color Purity of Monolithic Full Color Micro-LEDs Using Distributed Bragg Reflector and Blue Light Absorption Material
(2020-05-01)
Chu, Shao-Yu
;
Wang, Hung-Yu
;
Lee, Ching-Ting
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Lee, Hsin-Ying
;
Laing, Kai-Ling
In this study, CdSe/ZnS core-shell quantum dots (QDs) with various dimensions were used as the color conversion materials. QDs with dimensions of 3 nm and 5 nm were excited by gallium nitride (GaN)-based blue micro-light-emitting diodes (micro-LEDs) with a size of 30 mu m x 30 mu m to respectively form the green and red lights. The hybrid Bragg reflector (HBR) with high reflectivity at the regions of the blue, green, and red lights was fabricated on the bottom side of the micro-LEDs to reflect the downward light. This could enhance the intensity of the green and red lights for the green and red QDs/micro-LEDs to 11% and 10%. The distributed Bragg reflector (DBR) was fabricated on the QDs color conversion layers to reflect the non-absorbed blue light that was not absorbed by the QDs, which could increase the probability of the QDs excited by the reflected blue light. The blue light absorption material was deposited on the DBR to absorb the blue light that escaped from the DBR, which could enhance the color purity of the resulting green and red QDs/micro-LEDs to 90.9% and 90.3%, respectively.
Improved Linearity in AlGaN/GaN HEMTs for Millimeter-Wave Applications by Using Dual-Gate Fabrication
(2017-01-01)
Wang, Huan-Chung
;
Su, Huan-Fu
;
Luc, Quang-Ho
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Lee, Ching-Ting
;
Hsu, Heng-Tung
An effective method of improving the linearity of AlGaN/GaN HEMTs by using dual-gate technology is demonstrated. In this letter, we compare the DC characteristics and device linearity of the dual-gate AlGaN/GaN HEMTs with conventional single-gate AlGaN/GaN HEMTs. The correlation between the extrinsic transconductance (Gm) with third-order intermodulation distortion (IM3) and third order intercept point (IP3) suggests that the broader Gm distribution as a function of gate-bias, causes a lower IM3 level and higher IP3 values for the device. The improved device linearity demonstrates that dual-gate AlGaN/GaN HEMT design is a good approach for high-linearity RF device applications. (c) The Author(s) 2017. Published by ECS. All rights reserved.
Inductively coupled plasma grown semiconductor films for low cost solar cells with improved light-soaking stability
(2011-07-18)
Shen, Chang-Hong
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Shieh, Jia-Min
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Huang, Jung Y.
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Kuo, Hao-Chung
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Hsu, Chih-Wei
We investigate the performance of a single-junction amorphous Si (a-Si) solar cell fabricated with inductively coupled plasma (ICP) deposition technique. The high-density plasma resulting from high dissociation capacity of ICP enables good-quality hydrogenated Si films to be synthesized at low temperatures. High-density ICP also promotes the diffusion of reactive radicals on substrates and forms a-Si:H films with low defect density (similar to 3 x 10(15) cm(-3)). We demonstrate single-junction a-Si solar cells with a conversion efficiency of 9.6% and improved light-soaking stability. This low thermal-budget thin-film technique could open up the feasibility of efficient thin film solar cells on flexible substrates. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615650]
Investigation of the Flip-Chip Package With BCB Underfill for W-Band Applications
(2014-01-01)
Wang, Chin-Te
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Hsu, Li-Han
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Wu, Wei-Cheng
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Hsu, Heng-Tung
;
Chang, Edward Yi
Flip-chip package has great potential for use in millimeter-wave applications. However, the coefficient of thermal expansion mismatch between the chip and the substrate usually generates thermal stresses that fracture the flip-chip structure. The use of underfills with low dielectric loss is essential to improve the mechanical strength and reliability of the flip-chip package. Benzocyclobutene (BCB) was used in this study as the underfill material for the flip-chip structure using the no-flow process. The flip-chip structure with BCB injection provides good RF performance with a return loss of better than 18 dB and an insertion loss of 0.6 dB up to 100 GHz, in addition to a lower dielectric loss. Furthermore, thermal cycle and shear force tests show that the underfill injection can significantly improve the reliability of a flip-chip package.
Low Temperature a-SiGe:H Near-IR Sensor and Photovoltaic Devices for Flexible Multi-functional Panel
(2013-01-01)
Kao, Ming-Hsuan
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Shieh, Jia-Min
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Shen, Chang-Hong
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Yu, Peichen
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Kuo, Hao-Chung
High Near-IR response photo-diode (0.1A/W@800nm) and high efficiency a-Si/a-SiGe tandem solar cell (8.38%) were demonstrated using high-density plasma-fabricated a-SiGe:H deposition technology with Si2H6 and GeH4 precursor. The low temperature (140 degrees C) a-SiGe: H films with low defect density (2.3x10(16)cm(-3)) are suitable for the applications of flexible solar self-powered multi-functional panel and 3D stacked monolithic devices.
Multi-functional stacked light-trapping structure for stabilizing and boosting solar-electricity efficiency of hydrogenated amorphous silicon solar cells
(2013-08-12)
Huang, Wen-Hsien
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Shieh, Jia-Min
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Pan, Fu-Ming
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Shen, Chang-Hong
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Huang, Jung Y.
A sandwiched light-trapping electrode structure, which consists of a capping aluminum-doped ZnO (AZO) layer, dispersed plasmonic Au-nanoparticles (Au-NPs), and a micro-structured transparent conductive substrate, is employed to stabilize and boost the conversion-efficiency of hydrogenated amorphous silicon (a-Si:H) solar cells. The conformal AZO ultrathin layer (5 nm) smoothened the Au-NP-dispersed electrode surface, thereby reducing defects across the AZO/a-Si:H interface and resulting in a high resistance to photo-degradation in the ultraviolet-blue photoresponse band. With the plasmonic light-trapping structure, the cell has a high conversion-efficiency of 10.1% and the photo-degradation is as small as 7%. (C) 2013 AIP Publishing LLC.
Near-omni-directional sub-micron Silica light-trapping monolayer for amorphous Si photovoltaic devices
(2011)
Huang, Wen-Hsien
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Shieh, Jia-Min
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Shen, Chang-Hong
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Huang, Jung Y.
;
Kuo, Hao-Chung
The non-closely packed (surface-coverage of 55-65%) sub-micron silica sphere (400 nm) light-trapping monolayer was introduced to boost photocurrent (efficiency) of thin film amorphous solar cells by 15% (6.9%). The enhancement is nearly omni-directional.