Browsing by Author "Chang, Chia-Hua"

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A 135-mW Fully Integrated Data Processor for Next-Generation Sequencing
(2017-12-01)
Wu, Yi-Chung
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Chang, Chia-Hua
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Hung, Jui-Hung
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Yang, Chia-Hsiang
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分子醫學與生物工程研究所
Next-generation sequencing (NGS) enables high-throughput sequencing, in which short DNA fragments can be sequenced in a massively parallel fashion. However, the essential algorithm behind the succeeding NGS data analysis, DNA mapping, is still excessively time consuming. DNA mapping can be partitioned into two parts: suffix array (SA) sorting and backward searching. Dedicated hardware designs for the less-complex backward searching have been proposed, but feasible hardware for the most complicated part, SA sorting, has never been explored. Based on the memory-efficient sBWT algorithm, this work is the first integrated NGS data processor for the entire DNA mapping. The k-ordered Ferragina and Manzini index used in the sBWT algorithm is leveraged to improve storage capacity and reduce hardware complexity. The proposed NGS data processor realizes the sBWT algorithm through bucket sorting, suffix grouping, and suffix sorting circuits. Key design parameters are analyzed to achieve the optimal performance with respect to hardware cost and execution time. Fabricated in 40-nm CMOS, the NGS data processor dissipates 135 mW at 200 MHz from a 0.9-V supply. With 1-GB external memory, the chip can analyze human DNA within 10 min. This work achieves 43 065x and 8 971x [3208x and 402x] higher energy efficiency (throughput-to-area ratio) than the high-end CPU and GPU solutions, respectively.
Angle-resolved characteristics of silicon photovoltaics with passivated conical-frustum nanostructures
(2011-09-01)
Tseng, Ping-Chen
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Yu, Peichen
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Chen, Hsin-Chu
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Tsai, Yu-Lin
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Han, Hao-Wei
Passivation plays a critical role in silicon photovoltaics, yet how a passivation layer affects the optical characteristics of nano-patterned surfaces has rarely been discussed. In this paper, we demonstrate conical-frustum nanostructures fabricated on silicon solar cells using polystyrene colloidal lithography with various silicon-nitride (SiN(x)) passivation thicknesses. The omnidirectional and broadband antireflective characteristics were determined by utilizing angle-resolved reflectance spectroscopy. The conical-frustum arrays with a height of 550 nm and a SiN(x) thickness of 80 nm effectively suppressed the Fresnel reflection in the wavelength range from 400 to 1000 nm, up to an incidence angle of 60 degrees. As a result, the power conversion efficiency achieved was 13.39%, which showed a 9.13% enhancement compared to that of a conventional KOH-textured silicon cell. The external quantum efficiency measurements confirmed that the photocurrent was mostly contributed by the increased optical absorption in the near-infrared. The angular cell efficiencies were estimated and showed improvements over large angles of incidence. (C) 2011 Elsevier B.V. All rights reserved.
Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes
(2011-02-14)
Hsu, Min-Hsiang
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Yu, Peichen
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Huang, Jen-Hsien
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Chang, Chia-Hua
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Wu, Chien-Wei
In this paper, we present evidence of balanced electron and hole transport in polymer-fullerene based solar cells by means of embedded indium-tin-oxide nanoelectrodes. Enabled by a controllable electrochemical deposition, the individual nanoelectrodes are uniformly enclosed by a poly (3,4-ethylenedioxythiophene) hole-conducting layer, allowing a relatively short route for holes to reach the anode and hence increasing the effective hole mobility. Consequently, the power conversion efficiency and photogenerated current are maximized with a deposition condition of 50 mu C, where the ratio of the electron to hole mobility is nearly unity. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556565]
Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes (vol 98, 073308, 2011)
(2011-03-14)
Hsu, Min-Hsiang
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Yu, Peichen
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Huang, Jen-Hsien
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Chang, Chia-Hua
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Wu, Chien-Wei
Combined micro- and nano-scale surface textures for enhanced near-infrared light harvesting in silicon photovoltaics
(2011-03-04)
Chang, Chia-Hua
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Yu, Peichen
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Hsu, Min-Hsiang
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Tseng, Ping-Cheng
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Chang, Wei-Lun
As silicon photovoltaics evolve towards thin-wafer technologies, efficient optical absorption for the near-infrared wavelengths has become particularly challenging. In this work, we present a solution that employs combined micro- and nano-scale surface textures to increase light harvesting in the near-infrared for crystalline silicon photovoltaics, and discuss the associated antireflection and scattering mechanisms. The surface textures are achieved by uniformly depositing a layer of indium-tin-oxide nanowhiskers on micro-grooved silicon substrates using electron-beam evaporation. The nanowhiskers facilitate optical transmission in the near-infrared by functioning as impedance matching layers with effective refractive indices gradually varying from 1 to 1.3. Materials with such unique refractive index characteristics are not readily available in nature. As a result, the solar cell with combined textures achieves over 90% external quantum efficiencies for a broad wavelength range of 460-980 nm, which is crucial to the development of advanced thin-substrate silicon solar cells.
Effect of Graded AlxGa1-xN Layers on the Properties of GaN Grown on Patterned Si Substrates
(2012-02-01)
Hsiao, Yu-Lin
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Lu, Lung-Chi
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Wu, Chia-Hsun
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Chang, Edward Yi
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Kuo, Chien-I
2.2-mu m-thick crack-free GaN films were grown on patterned Si substrates. The crack-free GaN films were obtained by patterning Si substrate and optimizing the graded AlxGa1-xN layers. With the increase of the graded AlxGa1-xN layer thickness, the GaN crystal quality improved as judged from the X-ray diffraction data. By applying multi-AlxGa1-xN layers on the patterned Si substrate, a 31% reduction of tensile stress for the GaN film was obtained as measured by micro-Raman. For the AlGaN/GaN high electron mobility transistor grown on 1 x 1 cm(2) larger patterns, the device exhibits maximum drain current density of 776 mA/mm and maximum transconductance of 101 mS/mm. (c) 2012 The Japan Society of Applied Physics
Effect of Postdeposition Annealing Temperatures on Electrical Characteristics of Molecular-Beam-Deposited HfO2 on n-InAs/InGaAs Metal-Oxide-Semiconductor Capacitors
(2012-02-01)
Trinh, Hai-Dang
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Lin, Yueh-Chin
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Wang, Huan-Chung
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Chang, Chia-Hua
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Kakushima, Kuniyuki
The electrical characteristics of molecular-beam-deposited HfO2/n-InAs/InGaAs metal-oxide-semiconductor capacitors with different postdeposition annealing (PDA) temperatures (400-550 degrees C) are investigated. Results show that the sample with the PDA temperature of 500 degrees C exhibits the best capacitance-voltage (C-V) behavior with small frequency dispersion and small hysteresis. The X-ray photoelectron spectroscopy (XPS) spectra show the reduction of the amount of As-related oxides to below the XPS detection level when the PDA temperature is up to 500 degrees C. As the PDA temperature was increased to above 500 degrees C, As and In atoms seem to diffuse significantly into HfO2, resulting in the degradation of C-V behavior. (C) 2012 The Japan Society of Applied Physics
Effect of Thermal Treatments on HfO2/In0.7Ga0.3As Metal-Oxide-Semiconductor Capacitor Characteristics
(2010)
Chang, Chia-Hua
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Shie, Tin-En
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Lin, Yueh-Chin
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Kakushima, K.
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Iwai, H.
Post deposition annealing is a critical process for the quality improvement of gate oxides on III-V MOS capacitors. Though high temperature annealing would effectively repair defects, it could also induce undesired electrical characteristics due to the crystallization of the gate oxide. In this work, we investigate the novel two steps annealing technique to improve the HfO2/In0.7Ga0.3As MOSCAP properties. The two steps process takes advantage of 1st high temperature annealing (550 degrees C) to improve the interface quality and 2nd low temperature annealing (450 degrees C) for curing bulk oxide without oxide crystallization. The two steps annealing technique greatly improves the HfO2/In0.7Ga0.3As properties as compared to single step process and is expected to be helpful for future III-V MOSFET development.
Effective Passivation With High-Density Positive Fixed Charges for GaN MIS-HEMTs
(2017-05-01)
Liu, Shih-Chien
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Huang, Chung-Kai
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Chang, Chia-Hua
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Lin, Yueh-Chin
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Chen, Bo-Yuan
An effective passivation with high-density positive fixed charges was demonstrated on GaN MIS-HEMTs. The positive fixed charges at the interface between passivation and AlGaN surface can reduce the surface potential and expand the quantum well under Fermi level. Besides, to satisfy charge balance, the net charge density at the AlGaN surface must equal to the 2DEG carrier density. Thus, the positive fixed charges passivation can increase the 2DEG carrier density and improve the switching performance of GaN MIS-HEMTs. In this paper, we demonstrated a high-density positive fixed charges (similar to 2.71 x 10(13) e/cm(-2)) passivation using SiON for GaN MIS-HEMTs. The device with SiON passivation exhibits significant improvements in I-V characteristics and dynamic R-ON compared to the conventional SiN passivated device.
Efficiency Enhancement of GaAs Photovoltaics Employing Antireflective Indium Tin Oxide Nanocolumns
(2009-04-27)
Yu, Peichen
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Chang, Chia-Hua
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Chiu, Ching-Hua
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Yang, Chin-Sheng
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Yu, Jue-Chin
Highly-oriented indium tin oxide nano-columns are prepared by glancing-angle deposition with nitrogen. The tapered column profiles, which function as a graded-refiractive-index layer, offer superior antireflective characteristics. The nano-structured material serves as the conductive antireflective layer for GaAs solar cells, demonstrating a viable efficiency-boosting strategy for next-generation photovoltaics.
Embedded indium-tin-oxide nanoelectrodes for efficiency and lifetime enhancement of polymer-based solar cells
(2010-04-12)
Yu, Peichen
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Chang, Chia-Hua
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Su, Ming-Shin
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Hsu, Min-Hsiang
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Wei, Kung-Hwa
In this paper, distinctive indium-tin-oxide (ITO) nanorods are employed to serve as buried electrodes for polymer-based solar cells. The embedded nanoelectrodes allow three-dimensional conducting pathways for low-mobility holes, offering a highly scaffolded cell architecture in addition to bulk heterojunctions. As a result, the power conversion efficiency of a polymer cell with ITO nanoelectrodes is increased to about 3.4% and 4.4% under one-sun and five-sun illumination conditions, respectively, representing an enhancement factor of up to similar to 10% and 36% compared to a conventional counterpart. Also, the corresponding device lifetime is prolonged twice as much to about 110 min under five-sun illumination.
Enhanced angular characteristics of indium tin oxide nanowhisker-coated silicon solar cells
(2011-05-09)
Chang, Chia-Hua
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Hsu, Min-Hsiang
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Tseng, Ping-Chen
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Yu, Peichen
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Chang, Wei-Lun
Omnidirectional and broadband light harvesting is critical to photovoltaics due to the sun's movement and its wide spectral range of radiation. In this work, we demonstrate distinctive indium-tin-oxide nanowhiskers that achieve superior angular and spectral characteristics for crystalline silicon solar cells using angle-resolved reflectance spectroscopy. The solar-spectrum weighted reflectance is well below 6% for incident angles of up to 70 and for the wavelength range between 400nm and 1000nm. As a result, the nanowhisker coated solar cell exhibits broadband quantum efficiency characteristics and enhanced short-circuit currents for large angles of incidence. (C) 2011 Optical Society of America
Enhanced efficiency for c-Si solar cell with nanopillar array via quantum dots layers
(2011-09-12)
Chen, Hsin-Chu
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Lin, Chien-Chung
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Han, Hao-Wei
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Tsai, Yu-Lin
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Chang, Chia-Hua
The enhanced efficiency of the crystalline silicon (c-Si) solar cell with nanopillar arrays (NPAs) was demonstrated by deployment of CdS quantum dots (QDs). The NPAs was fabricated by the colloidal lithography and reactive-ion etching techniques. Under a simulated one-sun condition, the device with CdS QDs shows a 33% improvement of power conversion efficiency, compared with the one without QDs. For further investigation, the excitation spectrum of photoluminescence (PL), absorbance spectrum, current-voltage (I-V) characteristics, reflectance and external quantum efficiency of the device was measured and analyzed. It is noteworthy that the enhancement of efficiency could be attributed to the photon down-conversion, the antireflection, and the improved electrical property. (C) 2011 Optical Society of America
Fabrication of AlGaN/GaN High Electron Mobility Transistors (HEMTs) on Silicon Substrate with Slant Field Plates Using Deep-UV Lithography Featuring 5W/mm Power Density at X-band
(2012)
Chang, Chia-Hua
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Hsu, Heng-Tung
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Huang, Lu-Che
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Chiang, Che-Yang
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Chang, Edward Yi
In this work, AlGaN/GaN HEMTs on silicon with slant field platehave been successfully fabricated using deep-UV lithography. By using an angle exposure technique, submicron T-shaped gates with slant sidewalls were achieved. The 0.6 x 100 mu m(2) slant-field-plated AlGaN/GaN HEMT on silicon substrate exhibited a peak value of transconductance of 214 mS/mm and a breakdown voltage of 122 V. Through high-frequency measurements, the device revealed a current gain cutoff frequency (f(T)) of 24 GHz, a maximum oscillation frequency (f(max)) of 49 GHz and an output power density of 5.0 W/mm at X-band.
Frequency-Dependent Complex Conductivities and Dielectric Responses of Indium Tin Oxide Thin Films from the Visible to the Far-Infrared
(2010-12-01)
Chen, Ching-Wei
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Lin, Yen-Cheng
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Chang, Chia-Hua
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Yu, Peichen
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Shieh, Jia-Min
Transparent and conducting indium tin oxide (ITO) thin films form an integral part for various optoelectronic devices. In this paper, we report the frequency-dependent complex conductivities and dielectric responses of several sputtered ITO thin films with thicknesses in the range of 189-962 nm by using terahertz time domain spectroscopy (THz-TDS), optical reflectance spectroscopy, and electrical measurements. The plasma frequencies are verified to be from 1590 to 1930 rad.THz, while the scattering times are in the range 6-7 fs based on the Drude free-electron model. The mobilities of the above ITO thin films are calculated to be 32.7-34.2 cm(2) V(-1) s(-1), whereas the carrier concentrations lie in the range 2.79-4.10 x 10(20) cm(-3). The electrical properties derived from the THz-TDS technique agree well with those determined by Hall measurement. Parameters for the complex dielectric function suitable for ITO in the range 0.2-2 and 4-450 THz are also determined.
High Efficiency Triple-Junction Solar Cells Employing Biomimetic Antireflective Structures
(2011)
Chiu, Meng-Yih
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Chang, Chia-Hua
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Chang, Feng-Yu
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Yu, Peichen
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光電工程學系
In this work, we demonstrate a thorough device design, fabrication, characterization, and analysis of biomimetic antireflective structures implemented on a Ga(0.5)In(0.5)P/GaAs/Ge triple-junction solar cell. The sub-wavelength structures are fabricated on a silicon nitride passivation layer using polystyrene nanosphere lithography followed by anisotropic etching. The fabricated structures enhance optical transmission in the ultraviolet wavelength range, compared to a conventional single-layer antireflective coating (ARC). The transmission improvement contributes to the enhanced photocurrent, which is also verified by the external quantum efficiency characterization of fabricated solar cells. Under one-sun illumination, the short-circuit current of a cell with a biomimetic structures is enhanced by 24.1% and 2.2% due to much improved optical transmission and current matching, compared to cells without an ARC and with a conventional ARC, respectively. Further optimizations of the biomimetic structures including the periodicity and etching depth are conducted by performing comprehensive calculations based on a rigorous couple-wave analysis method.
Improved efficiency for nanopillar array of c-Si photovoltaic by down-conversion and anti-reflection of quantum dots
(2012)
Lin, Chien-Chung
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Chen, Hsin-Chu
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Han, Hau-Vei
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Tsai, Yu-Lin
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Chang, Chia-Hua
Improvement of efficiency for crystalline silicon (c-Si) with nanopillar arrays (NPAs) solar cell was demonstrated by deployment of CdS quantum dots (QDs). The NPAs was fabricated by colloidal lithography of self-assembled polystyrene (PS) nanospheres with a 600 nm in size and reactive-ion etching techniques, and then a colloidal CdS QDs with a concentration of 5 mg/mL was spun on the surface of c-Si with NPAs solar cell. Under a simulated one-sun condition, the device with CdS QDs shows a 33% improvement of power conversion efficiency, compared with the one without QDs. Additionally, we also found that the device with CdS QDs shows a 32% reduction in electrical resistance, compared with the one without QDs solar cell, under an ultraviolet (UV) light of 355nm illumination. This reduced electrical resistance can directly contribute to our fill-factor (FF) enhancement. For further investigation, the excitation spectrum of photoluminescence (PL), absorbance spectrum, current-voltage (I-V) characteristics, reflectance and external quantum efficiency (EQE) of the device were measured and analyzed. Based on the spectral response and optical measurement, we believe that CdS QDs not only have the capability for photon down-conversion in ultraviolet region, but also provide extra antireflection capability.
NANOSTRUCTURED THIN-FILM FORMED BY UTILIZING OBLIQUE-ANGLE DEPOSITION AND METHOD OF THE SAME
(2010-10-14)
Chang, Chia-Hua
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Yang, Chin-Sheng
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Chiu, Ching-Hua
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Yu, Pei-Chen
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Kuo, Hao-Chung
The present invention discloses a transparent conductive nanostructured thin-film by oblique-angle deposition and method of the same. An electron beam system is utilized to evaporate the target source. Evaporation substrate is disposed on a plurality of adjustable sample stage. Multiple gas control valve and heat source is provided to control the gas flow and temperature within the process chamber. An annealing process is performed after the evaporation to improve the thin-film structure and optoelectronic properties.
Nanostructured thin-film formed by utilizing oblique-angle deposition and method of the same
(2010-02-18)
Chang, Chia-Hua
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Yang, Chin-Sheng
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Chiu, Ching-Hua
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Yu, Pei-Chen
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Kuo, Hao-Chung
The present invention discloses a transparent conductive nanostructured thin-film by oblique-angle deposition and method of the same. An electron beam system is utilized to evaporate the target source. Evaporation substrate is disposed on a plurality of adjustable sample stage. Multiple gas control valve and heat source is provided to control the gas flow and temperature within the process chamber. An annealing process is performed after the evaporation to improve the thin-film structure and optoelectronic properties.
Non-Drude Behavior in Indium-Tin-Oxide Nanowhiskers and Thin Films Investigated by Transmission and Reflection THz Time-Domain Spectroscopy
(2013-08-01)
Yang, Chan-Shan
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Lin, Mao-Hsiang
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Chang, Chia-Hua
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Yu, Peichen
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Shieh, Jia-Min
A comparative study of indium-tin-oxide (ITO) nanowhiskers (NWhs) and thin films as transparent conductors in the terahertz frequency range are conducted. We employ both transmission-type and reflection-type terahertz time-domain spectroscopies (THz-TDTS and THz-TDRS) to explore the far-infrared optical properties of these samples. Their electrical properties, such as plasma frequencies and carrier scattering times, are analyzed and found to be fitted well by the Drude-Smith model over 0.1-1.4 THz. Further, structural and crystalline properties of samples are examined by scanning electron microscopy and X-ray diffraction, respectively. Non-Drude behavior of complex conductivities in ITO NWhs is attributed to carrier scattering from grain boundaries and impurity ions. In ITO thin films, however, the observed non-Drude behavior is ascribed to scattering by impurity ions only. Considering NWhs and thin films with the same height, mobility of the former is similar to 125 cm(2) V-1 s(-1), much larger than those of the ITO thin films, similar to 27 cm(2) V-1 s(-1). This is attributed to the longer carrier scattering time of the NWhs. The dc conductivities (similar to 250 Omega(-1) cm(-1)) or real conductivities in the THz frequency region of ITO NWhs is, however, lower than those of the ITO thin films (similar to 800 Omega(-1) cm(-1)) but adequate for use as electrodes. Partly, this is a reflection of the much higher plasma frequencies of thin films. Significantly, the transmittance of ITO NWhs (congruent to 60%-70%) is much higher (congruent to 13 times) than those of ITO thin films in the THz frequency range. The underneath basic physics is that the THz radiation can easily propagate through the air-space among NWhs. The superb transmittance and adequate electrical properties of ITO NWhs suggest their potential applications as transparent conducting electrodes in THz devices.