Browsing by Author "Chang, YH"

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1.2V CMOS switched-capacitor circuits
(1996)
Wu, JT
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Chang, YH
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Chang, KL
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
1.3 mu m quantum dot vertical-cavity surface-emitting laser with external light injection
(2005-10-27)
Peng, PC
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Chang, YH
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Kuo, HC
;
Tsai, WK
;
Lin, G
A 1.3 mu m quantum dot vertical-cavity surface-emitting laser (QD VCSEL) with external light injection is presented, having been experimentally demonstrated. The QD VCSEL is fabricated on GaAs substrate. The 3 dB frequency response of the QD VCSEL based on the TO-Can package is enhanced from the free-running 1.75 to 7.44 GHz with the light injection technique.
1.3-mu m InAs-InGaAs quantum-dot vertical-cavity surface-emitting laser with fully doped DBRs grown by MBE
(2006-01-01)
Yu, HC
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Wang, JS
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Su, YK
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Chang, SJ
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Lai, FI
We report InAs-InGaAs quantum-dot vertical-cavity surface-emitting lasers (VCSELs) grown by molecular beam epitaxy with fully doped n- and p-doped AlGaAs distributed Bragg reflectors and including an AlAs layer to form a current and waveguiding aperture. The metal contacts are deposited on a topmost p(+) (GaAs)-Ga-. contact layer and on the bottom surface of the n(+)-GaAs substrate. This conventional selectively oxidized top-emitting device configuration avoids the added complexity of fabricating intracavity or coplanar ohmic contacts. The VCSELs operate continuous-wave at room temperature with peak output powers of 0.33 mW and differential slope efficiencies up to 0.23 W/A. The peak lasing wavelengths are near 1.275 mu m, with a sidemode suppression ratio of 28 dB.
10 Gb/s single-mode vertical-cavity surface-emitting laser with large aperture and oxygen implantation
(2004-08-01)
Lai, FI
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Hsueh, TH
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Chang, YH
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Kuo, HC
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Wang, SC
High-speed single transverse mode 850 nm vertical cavity surface emitting lasers (VCSELs) with large emission aperture with a diameter of 8 Am were fabricated. These VCSELs exhibit good performance with threshold currents of 1.5 mA, a single transverse mode emission within the full operational range and a maximum output power of 3.8 mW. The large aperture is advantageous to these VCSELs with a smaller dynamic resistance (60 Omega) than that of conventional single-mode VCSEL. These single-mode VCSELs also demonstrate superior high-speed performance up to 10 Gb s(-1).
10 Gbps InGaAs : Sb-G-aAs-GaAsP quantum well vertical cavity surface emitting lasers with 1.27 mu m emission wavelengths
(2005-04-01)
Chang, YH
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Kuo, HC
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Chang, YA
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Chu, JT
;
Tsai, MY
InGaAs:Sb-GaAs-GaAsP vertical cavity surface emitting lasers (VCSELs) with 1.27 mu m emission wavelength were grown by metal-organic chemical vapor deposition (MOCVD) and exhibited excellent performance and temperature stability. The threshold current changes from 1.8 to 1.1 mA and the slope efficiency falls less than similar to 35% as the temperature is increased from room temperature to 70 degrees C. With a bias current of only 5 mA, the 3 dB modulation frequency response was measured to be 8.36GHz, which is appropriate for 10Gb/s operation. The maximal bandwidth is measured to be 10.7GHz With a modulation current efficiency factor (MCEF) of similar to 5.25 GHz/(mA) 1/2. Bit error rates of less than 10(-12) are demonstrated for 10 Gb/s data transmission from 25 degrees C to 70'C. We also accumulated life test data up to 1000 h at 70 degrees C/10 mA.
A novel master switching method for electronic cam control with special reference to multi-axis coordinated trajectory following
(2006-02-01)
Chang, YH
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Chieng, WH
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Liao, CS
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Jeng, SL
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機械工程學系
Multi-axis coordinated trajectory following is important in CNC machines and metal cutting tools. Recently, flight simulators with electrical actuators have been in increasing demand. However, the coordinate control scheme affects the accuracy of the motion because motors have an insufficient load-capacity relative to the hydraulic actuators. The electronic cam (ECAM) is typically used to perform coordinated control. However, selection of the master may determine potentially very different characteristics of motion. This study proposes an automatic master switching method. The conditions and results of the master switching method for ECAM are detailed. The robustness and stability of the proposed control system is also demonstrated using the well-known structured perturbation analysis tool, mu. (c) 2005 Elsevier Ltd. All rights reserved.
A novel structural design for force/torque fingertip sensors
(1998-08-01)
Chang, YH
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Huang, YC
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Liu, YP
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Tsay, SM
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電子工程學系及電子研究所
This work presents a novel structural design of force/torque fingertip sensors for sensing planar forces. The resolution can be increased by reducing the condition number of the calibration matrix and the sensitivity can be enhanced by placing strain gauges at specified positions. Moreover, the interaction from off-axis loads is intrinsically negligible in our design. A relatively simple and accurate calibration method for performance evaluation is introduced. Some experimental results are presented to demonstrate the capability of the proposed design.
A pretreatment technique to improvement the ashing resistance of low k spin-on-polymer (SOP)
(1999)
Chang, KM
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Yang, JY
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Chang, YH
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The oxygen plasma via resists strip process cause significant damage to organic SOP, thus limiting its inter-level dielectric application. A simple treatment technology using reactive ion is proposed to reform the SOP surface. The reactive ion modification of the SOP can improve the resistance towards oxygen plasma. This is owing to the carbon atom absence in the SOP's surface area. The measurements of Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), stress, thickness variation, Scanning Electron Microscope (SEM) cross-sectional view for gap filling and dielectric constant show that SOP with reactive ion treatment (RIT) has better quality for non-etch-back process than SOP without RIT.
Alignment error evaluation of the dial pattern
(1998-09-01)
Chang, YH
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Huang, YC
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
To achieve smooth etched sidewall surface at minimal time expense and reduce undercut etching are basic disciplines of the task of accurate alignment. When aligning etch-masks to [110] crystal orientation on a [100] Si wafer, a consideration is proposed by Schroder who uses a dial pattern for pre-etching to determine [110] crystal orientation. But that performance depends strongly on the resolution of the mask pattern generator. In this paper, we analyse Schroder's method by mathematical modeling and computer simulation. Finally, we propose an improvement for the Schroder limitation according to our analytic results.
An investigation of bias temperature instability in hydrogenated low-temperature polycrystalline silicon thin film transistors
(2002-09-01)
Lin, CW
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Tseng, CH
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Chang, TK
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Chang, YH
;
Chu, FT
The instability mechanisms of the hydrogenated n-channel low-temperature polycrystalline silicon thin film transistors under on-state stress were investigated with various bias stress conditions and device channel widths. It was found that hot carrier degradation which originated from a high drain electric field and self-heating during high current operation were the two dominant mechanisms responsible for device degradation. An electrically reversible depassivation/passivation phenomenon was also found in devices under high current stress. but not in those under hot carrier stress. It was inferred that the self-heating effect would accelerate the bond breakage and diffusion of hydrogen ions, thus enhancing the rate of depassivation/passivation. Moreover. when the Current in the hot carrier stress mode was sufficiently high. self-heating became the dominant degradation mechanism and hot carrier degradation phenomenon was also suppressed for devices with large channel width, Meanwhile, the electrically reversible depassivation/passivation phenomenon also occurred in this case.
Characterization of InGaN/GaN multiple quantum well nanorods fabricated by plasma etching with self-assembled nickel metal nanomasks
(2005-04-01)
Hsueh, TH
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Huang, HW
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Kao, CC
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Chang, YH
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Ou-Yang, MC
High-density (3.0 x 1010 cm (-2)) InGaN/GaN Multiple quantum well (MQW) nanorods were fabricated from an as-grown bulk light-emitting diode structure by inductively coupled plasma dry etching with self-assembled nickel metal nanomasks. The self-assembled nickel metal nanomasks were formed by rapid thermal annealing of a nickel metal film at 850 degrees C for 1 min. The influence of the thicknesses of the Ni metal film on the dimensions and density of the nanorods was also investigated. The structural and optical properties of the InGaN/GaN MQW nanorods were established using field emission scanning electron microscopy, transmission electron microscopy and photoluminescence measurements. The diameters and heights of nanorods were estimated to be 60 to 100nm and more than 0.28 mu m, respectively. The peak emission wavelength of the nanorods showed a blue shift of 5.1 nm from that of the as-grown bulk. An enhancement by a factor of 5 in photoluminescence intensity of the nanorods compared with that of the as-grown bulk was observed. The blue shift is attributed to strain relaxation in the wells after dry etching, the quantum confinement effect, or a combination of the two, which results in the enhancement of emission intensity.
Chemical vapor deposition of tantalum carbide and carbonitride thin films from Me3CE=Ta(CH2CMe3)(3) (E = CH, N)
(2003)
Chang, YH
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Wu, JB
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Chang, PJ
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Chiu, HT
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應用化學系
Chemical vapor deposition (CVD) of thin films employing Me3CCH=Ta(CH2CMe3)(3) and Me3CN=Ta(CH2CMe3)(3) as the precursors has been carried out. TaC and TaCN films were deposited at relatively low temperatures (623-923 K). In comparison, using Me3CN=Ta(CH2CMe3)(3), the Ta=N bond did not undergo cleavage during the reaction and the N atom was incorporated into the film as nitride. The volatile components evolved were collected and examined by GC-MS, FT-IR, H-1 and C-13 NMR spectroscopy. Possible decomposition pathways of the tantalum complexes are proposed to rationalize the observation.
Dynamic characteristics of long-wavelength quantum dot vertical-cavity surface-emitting lasers with light injection
(2006-04-03)
Peng, PC
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Kuo, HC
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Tsai, WK
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Chang, YH
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Lin, CT
This investigation experimentally demonstrates the dynamic characteristics of quantum dot vertical-cavity surface-emitting lasers (QD VCSEL) without and with light injection. The QD VCSEL is fully doped structure on GaAs substrate and operates in the 1.3 mu m optical communication wavelength. The eye diagram, frequency response, and intermodulation distortion are presented. We also demonstrate that the frequency response enhancement by light injection technique allows us to improve the performance of subcarrier multiplexed system. (c) 2006 Optical Society of America.
Effect of annealing on low-threshold-current large-wavelength InGaAs quantum well vertical-cavity laser
(2006-02-01)
Chen, IL
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Hsu, WC
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Kuo, HC
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Sung, CP
;
Chiou, CH
An emission wavelength record emission wavelength of 1245 nm in double InGaAs/GaAs quantum wells without a strain-compensated barrier is obtained by metalorganic chemical vapor deposition (MOCVD). The effect of annealing on highly strained InGaAs quantum wells is analyzed using phtoluminanescence spectra. By comparing devices p-type distributed Bragg reflector (p-DBR) growth temperatures, the preliminary results indicate that a device with a low p-DBR growth temperature of 670 degrees C exhibits a low threshold current and a high light output power. A threshold current of 6.7 mA in an InGaAs vertical-cavity surface emitting laser (VCSEL) in CW operation is realized with an emission spectrum up to 1.26 mu m.
Enhancement of Subnikov-de Haas oscillations by microwave radiation
(1997-12-01)
Fan, JC
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Chang, YH
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Chen, YF
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Whang, JF
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Fang, FF
We report for the first time that the Subnikov-de Haas (SdH) pattern can be greatly enhanced by recording the changes in the quantum oscillations of magnetoresistance due to microwave radiation. In order to understand the origin of the enhancement, the dependence of the enhanced SdH signal on temperature, microwave frequency and power has been studied. It is concluded that the enhancement can be attributed to the effects of free carrier absorption and the suppression of the nonoscillatory magnetoresistance. The technique shown here can be used to detect the SdH oscillations at relatively high temperature and in samples with moderate mobilities without perturbing the carrier concentration.
Fabrication and characteristics of high-speed oxide-confined VCSELs using InGaAsP-InGaP strain-compensated MQWs
(2004-12-01)
Chang, YH
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Kuo, HC
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Lai, FI
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Chang, YA
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Lu, CY
This paper presents the fabrication and characteristics of high-performance 850-mn InGaAsP-InGaP strain-compensated multiple-quantum-well (MQW) vertical-cavity surface-emitting lasers (VCSELs). The InGaAsP-InGaP MQW's composition was optimized through theoretical calculations, and the growth condition was optimized using photoluminescence. These VCSELs exhibit superior performance with characteristics threshold currents similar to0.4 mA and slope efficiencies similar to0.6 mW/mA. The threshold current change with temperature is less than 0.2 mA, and the slope efficiency drops less than similar to30% when the substrate temperature is raised from room temperature to 85degreesC. A high modulation bandwidth of 14.5 GHz and a modulation current efficiency factor of 11.6 GHz/(mA) (1/2) are demonstrated. The authors have accumulated life test data up to 1000 h at 70degreesC/8 mA.
Fabrication and characterization of In(0.25)Ga(0.75)N/GaN multiple quantum wells embedded in nanorods
(2005-10-01)
Hsueh, TH
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Sheu, JK
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Huang, HW
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Chang, YH
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Ou-Yang, MC
ln(0.25)Ga(0.75)N/GaN multiple quantum wells embedded in nanorods with diameters of 60-100nm were fabricated by inductively coupled plasma reactive ion etching with Cl(2)/Ar plasma. The strong optical emission of the nanorods, observed by micro-photoluminescence measurement at 80 K, reveals a large blue shift of about 90meV and an increase in photoluminescence intensity density of more than 17-fold, compared with that of the as-grown wafer under the same excitation power density of 80W/cm(2). These nanostructures have a high potential for application in efficient GaN-based vertical cavity emitters.
Fabrication and characterization of In0.25Ga0.75N/GaN multiple quantum wells embedded in nanorods
(2005-10-01)
Hsueh, TH
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Sheu, JK
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Huang, HW
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Chang, YH
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Ou-Yang, MC
ln(0.25)Ga(0.75)N/GaN multiple quantum wells embedded in nanorods with diameters of 60-100nm were fabricated by inductively coupled plasma reactive ion etching with Cl-2/Ar plasma. The strong optical emission of the nanorods, observed by micro-photoluminescence measurement at 80 K, reveals a large blue shift of about 90meV and an increase in photoluminescence intensity density of more than 17-fold, compared with that of the as-grown wafer under the same excitation power density of 80W/cm(2). These nanostructures have a high potential for application in efficient GaN-based vertical cavity emitters.
Fabrication and micro-photoluminescence investigation of Mg-doped gallium nitride nanorods
(2005-04-01)
Chang, YH
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Hsueh, TH
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Lai, FI
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Chang, CW
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Yu, CC
High-density magnesium (Mg)-doped gallium nitride (GaN) nanorods were fabricated by inductively coupled plasma reactive ion etching from a GaN film and had a mean length of approximately 50nm. A large blue-shift was observed in the photoluminescence (PL) peak energy of Mg-doped GaN nanorods under HeCd laser (325 nm) excitation. The PL spectra of the nanorods show a typical donor-acceptor-pair (DAP) emission at approximately 3.0 eV with a large blue-shift compared to that of the Mg-doped GaN film. The blue-shift energy increases from 8 meV to 67 meV as the excitation intensity varies from 12 kW/cm(2) to 56 kW/cm(2). Possible reasons for the power dependence of the spectral shift in the PL emission energy are discussed.
Fabrication and performance of blue GaN-based vertical-cavity surface emitting laser employing AlN/GaN and Ta2O5/SiO2 distributed Bragg reflector
(2005-08-22)
Kao, CC
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Peng, YC
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Yao, HH
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Tsai, JY
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Chang, YH
GaN-based vertical-cavity surface emitting laser with 3 lambda cavity and hybrid mirrors, consisting of the 25 pairs AlN/GaN dielectric Bragg reflector and the 8 pairs Ta2O5/SiO2, was fabricated. The laser action was achieved under the optical pumping at room temperature with a threshold pumping energy density of about 53 mJ/cm(2). The laser emits 448 nm blue wavelength with a linewidth of 0.25 nm and the laser beam has a degree of polarization of about 84%. (c) 2005 American Institute of Physics.