Browsing by Author "Lee, SC"

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A dopant-related defect in Te-doped AlInP
(1999-08-01)
Wu, YR
;
Sung, WJ
;
Wen, TC
;
Lee, SC
;
Lee, WI
A deep level in Te-doped Al0.5In0.5P, grown by metal organic chemical vapor deposition, has been studied by deep level transient spectroscopy. The thermal activation energy was 0.24 eV, and the trap concentration was related to Te-dopant concentration. The deep level concentration strongly increased with elevating Te-dopant concentration. Meanwhile, the trap distribution profile also presented the same distribution behavior as the Te concentration profile. Therefore, the deep level in Te-doped AlInP is verified to be a dopant-related defect.
A modified interpolated cell mapping method
(1997-01-16)
Ge, ZM
;
Lee, SC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A modified interpolated cell mapping (MICM) method is developed for global analysis of deterministic dynamical systems with smooth basin boundaries. By improving the algorithm of the interpolated cell mapping (ICM) and including the idea of sampling mappings of cells from the generalized cell mapping (GCM), MICM gives a more complete and precise global analysis of systems than ICM. In addition, based on analysis using MICM, a method using exact mappings is proposed to remedy the inaccuracy and incompleteness of global analysis due to interpolated mappings and the assumption of the sink cell. For the three systems studied in this paper, this method locates identical attractors and basins of attraction as the integration of a grid of points (IGP) method, with a 100-fold improvement in computational efficiency. (C) 1997 Academic Press Limited.
Activation of p-type GaN in a pure oxygen ambient
(2001-05-15)
Wen, TC
;
Lee, SC
;
Lee, WI
;
Chen, TY
;
Chan, SH
In this study, we activated p-type GaN in a pure oxygen ambient by rapid thermal annealing. The sheet resistance of p-type GaN was greatly reduced from > 10(7) Omega/square to 7.06 x 10(4) Omega/square after annealing in oxygen ambient at 500 degreesC, The photoluminescence intensity of blue emission increased by one order of magnitude compared to the as-grown sample. Moreover, the sheet resistance of p-type GaN annealed in pure oxygen ambient is lower than that of p-type GaN annealed in nitrogen ambient. The carrier concentrations of the samples annealed in oxygen ambient are higher than those annealed in nitrogen ambient. The better activation of p-type GaN in oxygen ambient is due to the higher activity of oxygen than that of nitrogen. Oxygen would remove hydrogen that passivates Ma atoms by forming H2O at a lower temperature.
Analysis of random dynamical systems by interpolated cell mapping
(1996-07-25)
Ge, ZM
;
Lee, SC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A method of interpolated cell mapping (ICM) is developed for global analysis of random dynamical systems. In this method, one first analyzes a random system by constructing a uniform number of sample interpolated trajectories for each cell. More sample interpolated trajectories are then constructed for critical cells sensitive to random effects to characterize the global behaviour of the system. When applied to the global analysis of non-linear systems with uncertain external loadings or system parameters, the proposed method yields more precise results than the generalized cell mapping (GCM) method. These results agree well with those obtained by Monte Carlo simulation. Additionally, the proposed method allows global analyses of random systems to be improved easily when the original regions of study are too large to give precise analyses. (C) 1996 Academic Press Limited
Analysis of random dynamical systems by interpolated cell mapping
(1996-07-25)
Ge, ZM
;
Lee, SC
;
機械工程學系
;
Department of Mechanical Engineering
A method of interpolated cell mapping (ICM) is developed for global analysis of random dynamical systems. In this method, one first analyzes a random system by constructing a uniform number of sample interpolated trajectories for each cell. More sample interpolated trajectories are then constructed for critical cells sensitive to random effects to characterize the global behaviour of the system. When applied to the global analysis of non-linear systems with uncertain external loadings or system parameters, the proposed method yields more precise results than the generalized cell mapping (GCM) method. These results agree well with those obtained by Monte Carlo simulation. Additionally, the proposed method allows global analyses of random systems to be improved easily when the original regions of study are too large to give precise analyses. (C) 1996 Academic Press Limited
Comments on "Parametric analysis and fractal-like basins of attraction by modified interpolated cell mapping" - Author's reply
(2004-05-06)
Ge, ZM
;
Lee, SC
;
機械工程學系
;
Department of Mechanical Engineering
Comprehensive investigation on fluorosilicate glass prepared by temperature-difference-based liquid-phase deposition
(2000-01-01)
Yeh, CF
;
Lee, YC
;
Wu, KH
;
Su, YC
;
Lee, SC
This study investigates the properties of fluorosilicate glass film prepared by temperature-difference-based liquid-phase deposition. Experimental results indicate that the deposition temperature can significantly affect the deposition rate and film properties. As the deposition temperature increases from 15 to 35 degrees C, the deposition rate increases exponentially from 30 to 687 Angstrom/h. Meanwhile, the F and OH contents increase from 2.56 to 3.49% and from 0.16 to 0.5%, respectively. The dielectric constants;ind stresses for the films deposited at 15, 25, and 35 degrees C, are 3.56/63 MPa, 3.46/43 MPa, and 3.66/73 MPa, respectively. The current densities at 2 MV/cm for the films deposited at 15, 25, and 35 degrees C are 6.9 x 10(-9), 4.6 x 10(-9), and 3.6 x 10(-7) A/cm(2), respectively. For the film deposited at 25 degrees C. the dielectric constant and the stress are minimal because of the high F content, low OH content, and low bond strain. The properties are also compared with those of fluorosilicate glass prepared by plasma-enhanced chemical vapor deposition. In addition to exhibiting a lower dielectric constant and much better resistance to moisture, the film prepared by temperature-difference-based liquid-phase deposition also shows a comparable or better insulating property, revealing a reliable intermetal dielectric with a low dielectric constant. (C) 2000 The Electrochemical Society. S0013-4651(99)04-019-7. All rights reserved.
Electrooptical properties of GaNAs/GaAs multiple quantum well structures
(2003-07-25)
Lee, JR
;
Chen, YY
;
Lu, CR
;
Lee, WI
;
Lee, SC
The electrooptical properties of the GaNAs/GaAs multiple quantum well structures have been studied using the photoreflectance spectroscopy from 20 K to room temperature. Above the band gap energy of GaAs, Franz-Keldysh oscillations were observed. The period of the Franz-Keldysh oscillations decreased slightly with decreasing temperature, and indicated that the corresponding space charge distribution varied slowly with temperature. The modulated quantum well transition features were observed below the band gap energy of GaAs. A matrix transfer algorithm was used to calculate the quantum well subband energies numerically. The band gap energy and the electron effective mass of the GaNAs/GaAs system were adjusted to obtain the subband energies to best fit the observed quantum well transition energies. (C) 2003 Elsevier Science B.V. All rights reserved.
Ga0.5In0.5P barrier layer for wet oxidation of AlAs
(2000-05-01)
Lee, SC
;
Lee, WI
;
電子物理學系
;
Department of Electrophysics
We study the stability of Ga0.5In0.5P acid Al0.4Ga0.6As barrier layers for wet thermal oxidation of AlAs on GaAs. Samples with a Ga0.5In0.5P or Al0.4Ga0.6As barrier layer are oxidized in a water vapor environment under various oxidation conditions. The results of photoluminescence and secondary-ion mass spectrometry (SIMS) depth profile measurements indicate that the Ga0.5In0.5P barrier layer is more stable than the Al0.4Ga0.6As layer at higher oxidation temperatures and longer periods of oxidation time.
Influence of barrier growth temperature on the properties of InGaN/GaN quantum wells
(2001)
Wen, TC
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Lee, SC
;
Lee, WI
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
This study invests the effect of barrier growth temperature on the properties of InGaN/GaN MQW. Increase the growth temperature will reduce the well thickness and result in the blue shift of the PL peak. This blue shift in FL peak wavelength may be resulted from the stain occure during varying barrier growth temperature rather than only the reduce the well width. Moreover, we introduce a phase separation enhance layer into InGaN/GaN MQW. This layer join with the variation of barrier growth temperature will enhance the phase separation in InGaN/GaN MQW. There are two peaks clearly revealed in RT PL spectra. The higher energy peak might originate the InGaN quasi-wetting layer on the GaN barrier surface. The other one is interpreted of localize state at potential fluctuation owning to phase separation.
Investigation of populated InAs/GaAs quantum dots by photoluminescence and photoreflectance
(2005-01-01)
Lee, JR
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Lu, CR
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Lee, WI
;
Lee, SC
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電子物理學系
We studied self-assembled InAs/GaAs quantum dots by contrasting photoluminescence and photoreflectance spectra from 10K to room temperature. The photoluminescence spectral profiles comprise contributions from four equally separated energy levels of InAs quantum dots. The emission profiles involving ground state and excited states have different temperature evolution. Abnormal spectral narrowing occurred above 200 K. In the photoreflectance spectra, major features corresponding to the InAs wetting layer and GaAs layers were observed. Temperature dependences of spectral intensities of these spectral features indicate that they originate from different photon-induced modulation mechanisms. Considering interband transitions of quantum dots were observed in photoluminescence spectra and those of wetting layer were observed in photoreflectance profiles, we propose that quantum dot states of the system are occupied up to the fourth energy level which is below the wetting layer quantum state. (C) 2004 Elsevier B.V. All rights reserved.
Mg-related deep levels in AlInP
(1999-07-01)
Wu, YR
;
Sung, WJ
;
Lee, SC
;
Li, TJ
;
Lee, WI
The properties of deep levels found in Mg-doped AlInP, grown by metal-organic chemical vapor deposition, have been studied. Two distinct levels, labeled E1 and E2, were observed, with the activation energy of 0.19 and 0.514 eV, respectively. From distribution profiles measured on trap E1, E2 and Mg-dopant, all three concentration profiles have similar behaviors. The concentration increases gradually from the interface of pn junction. Furthermore, both trap E1 and E2 concentration increase with elevating Mg-dopant concentration Thus, it seems that these deep levels originate from Mg-related defects.
Newly developed low-K and low-stress fluorinated silicon oxide utilizing temperature-difference liquid-phase deposition technology
(1998)
Yeh, CF
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Lee, YC
;
Lee, SC
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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
To meet the requirements of low-K and low-stress intermetal dielectric (IMD) for future ULSI devices, a novel temperature-difference liquid-phase deposition (TD-LPD) method is proposed. The deposition solution of supersaturated silicic acid with high concentration of fluorine can be achieved by raising deposition temperature larger than 15 degrees C from dissolution temperature (0 degrees C). Because fluorine atoms can easily be incorporated with the technique, TD-LPD fluorine-doped SiO2 (FSG) exhibits low-K (similar to 3.4) and low-stress (similar to 40MPa) property. In this paper, to study the interaction between TD-LPD FSG and moisture, the FSG is annealed and moisture stressed repeatedly as in a real process. Since K is sensitive to moisture absorption, and the stress is sensitive to the dehydration reaction between Si-OH's, the both are monitored as indices. A feasible mechanism is proposed to explain the variation in K/stress during annealing and boiling cycles.
Non-linear dynamics and chaos control of a damped satellite with partially-filled liquid
(1998-11-12)
Ge, ZM
;
Lee, CI
;
Chen, HH
;
Lee, SC
;
機械工程學系
The dynamic behaviors of a damped satellite with partially-filled liquid which is subjected to external disturbance are studied in this paper. The Lyapunov direct method is used to obtain conditions of stability of the equilibrium point of the system. A co-dimension one bifurcation analysis for the autonomous system is carried out near the degenerate point. It is found that Hopf bifurcation occurs in the system by center manifold theory. By applying numerical results, phase diagrams, power spectrum, Poincare maps, and Lyapunov exponents are presented to observe periodic and chaotic motions. The effect of the parameter changes in the system can be found in the bifurcation and parametric diagrams. For global analysis, the basins of attraction of each attractor of the system are located by employing the modified interpolated cell mapping (MICM) method. Finally, several methods, the delayed feedback control, the addition of constant motor torque, the addition of periodic force, and adaptive control algorithm are used to control chaos effectively. (C) 1998 Academic Press.
Non-linear dynamics and chaos control of a damped satellite with partially-filled liquid
(1998-11-12)
Ge, ZM
;
Lee, CI
;
Chen, HH
;
Lee, SC
;
機械工程學系
The dynamic behaviors of a damped satellite with partially-filled liquid which is subjected to external disturbance are studied in this paper. The Lyapunov direct method is used to obtain conditions of stability of the equilibrium point of the system. A co-dimension one bifurcation analysis for the autonomous system is carried out near the degenerate point. It is found that Hopf bifurcation occurs in the system by center manifold theory. By applying numerical results, phase diagrams, power spectrum, Poincare maps, and Lyapunov exponents are presented to observe periodic and chaotic motions. The effect of the parameter changes in the system can be found in the bifurcation and parametric diagrams. For global analysis, the basins of attraction of each attractor of the system are located by employing the modified interpolated cell mapping (MICM) method. Finally, several methods, the delayed feedback control, the addition of constant motor torque, the addition of periodic force, and adaptive control algorithm are used to control chaos effectively. (C) 1998 Academic Press.
Non-linear dynamics and chaos control of a physical pendulum with vibrating and rotating support
(2001-04-26)
Ge, ZM
;
Yang, CH
;
Chen, HH
;
Lee, SC
;
機械工程學系
The dynamic behavior of a physical pendulum system of which the support is subjected to both rotation and vertical vibration are studied in this paper. Both analytical and computational results are employed to obtain the characteristics of the system. By using Lyapunov's direct method the conditions of stability of the relative equilibrium position can be determined. Melnikov's method is applied to identify the existence of chaotic motion. The incremental harmonic balance method is used to find the stable and unstable periodic solutions For the strong non-linear system. By applying various numerical results such as phase portrait, Pioncare map. time history and power spectrum analysis, a variety of the periodic solutions and the phenomena of the chaotic motion can be presented. The effects of the changes of parameters in the system could be found in the bifurcation and parametric diagrams. Further, chaotic motion can be verified by using Lyapunov exponent and Lyapunov dimension. The global analysis of basin boundary and fractal structure are observed by the modified interpolated cell mapping method. Besides, non-feedback control, delayed feedback control, adaptive control, and variable structure control are used to control the chaos effectively. (C) 2001 Academic Press.
Nonlithographic random masking and regrowth of GaN microhillocks to improve light-emitting diode efficiency
(2006-01-01)
Lee, CL
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Lee, SC
;
Lee, WI
;
電子物理學系
;
友訊交大聯合研發中心
In this study, p-GaN microhillocks are grown on the top of a standard multiple-quantum-well (MQW) light-emitting diode (LED) with novel nonlithographic random masking. Such microhillocks can dramatically increase the external efficiency of the LED because of the destroyed symmetry of LED interfaces. By controlling metalorganic chemical vapor deposition (MOCVD) growth conditions, p-GaN microhillocks of various densities and sizes can be easily grown on a standard LED structure. The use of this novel method to grow microhillocks on the top of the LED can facilitate the control of the leakage current of LED compared that of the photo enhanced chemical (PEC) wet etch and inductively coupled plasma (ICP) dry etch methods.
Parametric analysis and fractal-like basins of attraction by modified interpolated cell mapping
(2002-06-06)
Ge, ZM
;
Tsen, PC
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Lee, SC
;
機械工程學系
;
Department of Mechanical Engineering
Phosphorus vacancy as a deep level in AlInP layers
(2000-06-15)
Sung, WJ
;
Wu, YR
;
Lee, SC
;
Wen, TC
;
Li, TJ
Deep levels in AlInP layers, grown by metal-organic chemical vapor deposition (MOCVD) with various V/III mole ratios, have been carefully investigated by deep-level transient spectroscopy (DLTS). A deep level originating from phosphorus vacancy was observed with the activation energy of 0.65 eV. Examining this phosphorus-vacancy-related deep level provided a relatively simple means of understanding the phosphorus vacancy in AlInP, thus allowing us to determine an appropriate V/III mole ratio for growing AlInP.
Photoreflectance characterization of GaNAs/GaAs multiple quantum well structures
(2002)
Lu, CR
;
Lee, JR
;
Chen, YY
;
Lee, WI
;
Lee, SC
We investigate GaNAs/GaAs multiple quantum well structures using the photoreflectance spectroscopy at various temperatures. The modulated optical response consists of quantum well excitonic transitions and band edge transitions that exhibits Franz-Keldysh oscillatory features. The bowing parameter, effective mass, and the band-offset value were adjusted to obtain the subband energies to best fit the observed quantum well transition energies. The period of the Franz-Keldysh oscillations indicates the strength of the internal field.