Browsing by Author "Chiang, CI"

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A high-temperature thermodynamic model for metalorganic vapor phase epitaxial growth of InGaN
(1999-09-01)
Ou, J
;
Pan, YC
;
Lee, WH
;
Shu, CK
;
Lin, HC
A thermodynamic analysis tailored with a high-temperature parameter was performed for metalorganic vapor phase epitaxial (MOVPE) growth of InxGa1-xN alloys. Accordingly, a series of InGaN samples were prepared under various input In flow rates and growth temperatures. Theoretical results indicate that the In solid concentration tends to increase with increasing In flow rate and with decreasing temperature, whereas the metal droplets form more easily on the surface at lower growth temperatures and higher In fluxes, which are in good agreement with our experimental data.
A revised minimum spanning table method for optimal expansion of competence sets
(2000)
Chiang, CI
;
Li, JM
;
Tzeng, GH
;
Yu, PL
;
運輸與物流管理系註：原交通所+運管所
Competence set analysis is a new approach to solve an import aspect of challenging MCDM problems. Thus, many researchers have developed efficient methods for solving the optimal expansion of competence sets (please see the references). The minimum spanning table method (MST) proposed by Feng and Yu (1997) is an efficient algorithm using spreadsheet tableaus to solve optimal expansion problems. In order to develop a computer program, in this paper, we propose the revised algorithm of MST, which can efficiently solve the optimal expansion problems. We develop a user-friendly program called MINST, which can solve fairly large-scale expanding problems even with PC of pentium 133.
An alternative formulation for certain fuzzy set-covering problems
(2005-08-01)
Chiang, CI
;
Hwang, MJ
;
Liu, YH
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
The fuzzy set-covering model using auxiliary 0-1 variables and a system of inequalities was developed by Hwang et al. [1]. By taking logarithm of the inequalities constraints and using the nature of the Boolean variables of this fuzzy set covering model, a simplified model is obtained. (c) 2005 Elsevier Ltd. All rights reserved.
Beryllium-implanted P-type GaN with high carrier concentration
(2001-05-01)
Yu, CC
;
Chu, CF
;
Tsai, JY
;
Lin, CF
;
Lan, WH
We report the results of beryllium implantation in Mg-doped GaN to obtain a high hole concentration and lower activation energy for Mg. The metal organic chemical vapor deposition (MOCVD)-grown Mg-doped GaN samples were implanted with Be ions at two different energies of 50 keV and 150 keV and a dose of 10(14) cm(-2). The implemented samples were subsequently annealed at 1100 degreesC for 60 s. The annealed samples showed an increase of hole concentration by three orders of magnitude from the non-implanted value of 5.5 x 10(16) to 8.1 x 10(19) cm(-3) as determined by Hall measurement. The activation energy of Mg dopants for the implanted annealed samples estimated from the temperature dependence of the photoluminescence data is about 170 meV, which is nearly 30% lower than that for the as-grown samples.
Competence set analysis - An effective means to solve non-trivial decision problems
(2001)
Chiang, CI
;
Yu, PL
;
管理學院
;
運輸與物流管理系註：原交通所+運管所
;
College of Management
Because of rapid change of our technology and environments many problems we are facing are new, complex, and nontrivial. The solutions to these problems are usually outside our day-to-day experience, competence, or our habitual domains. Thus, they are fuzzy and challenging. In order to effectively solve this kind of fuzzy or challenging problem, we need to continually expand our competence or habitual domains so that we can make a good decision with confidence. This paper is to describe a holistic picture of using competence set analysis to solve this kind of decision problem. First, two types of competence set analysis, problem-oriented and skill-oriented, are introduced. Next, the concept of selecting optimal competence set that maximizes the net return is discussed. We then briefly describe a number of algorithms to find the optimal path for expanding our competence set. Finally, we gave some applications of expanding competence set with minimum cost.
Gallium K-edge EXAFS study of GaN : Mg films
(2000)
Pan, YC
;
Wang, SF
;
Lee, WH
;
Lin, WC
;
Shu, CK
Ga K-edge extended X-ray absorption fine structure (EXAFS) measurement was employed to investigate the local structure of GaN:Mg films grown by metalorganic vapor phase epitaxy (MOVPE) with various Cp,Mg dopant flow rates using both in-plane and out-of-plane polarization modes of X-ray. The near edge absorption spectra were found to depend on X-ray polarization strongly for undoped GaN sample and weakly to minutely for heavily Mg-doped and amorphous films. The results indicate Mg incorporation modifies the local structure around the absorber Ga atom and, hence, alters the molecular orbital electron transition of GaN sample. EXAFS analysis showed both vacancy and Mg-interstitial defects contribute to the reduction of coordination numbers along the hexagonal c-axis of GaN:Mg film.
Gallium K-edge x-ray absorption study on Mg-doped GaN
(2001-01-01)
Pan, YC
;
Wang, SF
;
Lee, WH
;
Lee, MC
;
Chen, WK
Ga K-edge x-ray absorption measurements were employed to investigate Mg-doping effects in GaN samples. Strong polarization-dependent x-ray absorption near-edge structures become less pronounced with increasing doping concentration, indicating the formation of a mixing-phase structure of cubic and hexagonal phases. Analysis of the extended x-ray absorption region of the spectra revealed doping-related defects such as vacancies, substitutions, and interstitial occupations. They were formed anisotropically in the crystal c axis direction and its perpendiculars. Disorderliness arising from phase mix and defects is believed to have lowered the Debye temperature of the doped GaN films and caused the destructive interference of the absorption fine-structure oscillation functions. These effects were taken into account for the observed large coordination number reductions in our samples. (C) 2001 American Institute of Physics.
Influence of sapphire nitridation on properties of indium nitride prepared by metalorganic vapor phase epitaxy
(1999-02-01)
Pan, YC
;
Lee, WH
;
Shu, CK
;
Lin, HC
;
Chiang, CI
Indium nitride films have been successfully grown on (0001) sapphire substrates by metalorganic vapor phase epitaxy (MOVPE) using TMIn and NH3 as source precursors. Experimental results indicated that pregrowth treatments, such as buffer layer growth, nitridation temperature and nitridation duration have dramatic effects on the growth of the InN films. For films nitridated at 1,000 degrees C for 40 min without any buffer layer growth, we obtained an InN film quality with Hall mobility, carrier concentration and line width of Raman E-2 mode of 270 cm(2)/V.s, 5 x 10(19) cm(-3) and 4.5 cm(-1), respectively, which is among the best quality ever reported for such type of film grown by MOVPE.
Liquid phase deposited SiO2 on GaN
(2003-04-29)
Wu, HR
;
Lee, KW
;
Nian, TB
;
Chou, DW
;
Wu, JJH
An efficient and low cost approach to deposit uniform silicon dioxide layers on GaN by liquid phase deposition (LPD) near room temperature are described and discussed. The process is simple. GaN wafers are immersed into a H2SiF6 and H3BO3 solution to form the silicon dioxide layers. The deposition conditions and the properties of the SiO2 films will be characterized. (C) 2002 Elsevier Science B.V. All rights reserved.
Long-term photocapacitance decay behavior in undoped GaN
(2000)
Chung, HM
;
Pan, YC
;
Chung, WC
;
Chen, NC
;
Tsai, CC
We have employed the photocapacitance measurement to examine the physical properties of GaN Schottky diode made from the undoped epilayer grown by metalorganic vapor phase epitaxy. The resulted transient capacitance spectrum shows that the diode exhibits a characteristic of long-term logarithmic-type decaying behavior, which, we believe, is correlated closely to the linear arranged traps close to the core of the threading edge dislocations.
Optimal multiple stage expansion of competence set
(2000-02-01)
Li, JM
;
Chiang, CI
;
Yu, PL
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
In this paper, we consider the expansion processes of competence sets which have asymmetric cost functions, intermediate skills, and compound skills; among the skills, cyclic connections are possible. We introduce the concept of the stage expansion process (SEP) of the competence set, and provide mathematical programming methods to find a minimal cost SEP and the ordering of expansion. (C) 2000 Elsevier Science B.V. All rights reserved.
Structure study of GaN : Mg films by X-ray absorption near-edge structure spectroscopy
(2001)
Pan, YC
;
Wang, SF
;
Lee, WH
;
Lin, WC
;
Chiang, CI
X-ray absorption near-edge fine structure (XANES) spectroscopy from N K-edge measurement was employed to examine the crystal structure of metallorganic vapor phase epitaxy (MOVPE) grown Mg-doped GaN (GaN:Mg) films. The result showed that Mg doping induced crystal stacking faults to occur at the film surface causing a fraction of hexagonal phase to transform into cubic phase. As a consequence of this, XANES spectra of the films were found to vary with the dopant concentration and to lose pure hexagonal character when examined with the incident angle theta of the X-ray beam. Spectral characteristic variation between the two phases allows us to estimate the phase composition of the samples. The trend of increasing cubic phase component in dopant concentration is consistent with the observed Normaski optical micrograph. (C) 2001 Published by Elsevier Science Ltd.