Browsing by Author "Huang, HJ"

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A novel algorithm for uncertain portfolio selection
(2006-02-01)
Huang, HJ
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Tzeng, GH
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Ong, CS
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運輸與物流管理系註：原交通所+運管所
;
科技管理研究所
In this paper, the conventional mean-variance method is revised to determine the optimal portfolio selection under the uncertain situation. The possibilistic area of the return rate is first derived using the possibisitic regression model. Then, the Mellin transformation is employed to obtain the mean and the risk by considering the uncertainty. Next, the revised mean-variance model is proposed to deal with the problem of uncertain portfolio selection. In addition, a numerical example is used to demonstrate the proposed method. On the basis of the numerical results, we can conclude that the proposed method can provide the more flexible and accurate results than the conventional method under the uncertain portfolio selection situation. (c) 2005 Elsevier Inc. All rights reserved.
A novel hybrid model for portfolio selection
(2005-10-15)
Ong, CS
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Huang, HJ
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Tzeng, GH
;
科技管理研究所
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Institute of Management of Technology
As we know, the performance of the mean-variance approach depends on the accurate forecast of the return rate. However, the conventional method (e.g. arithmetic mean or regression-based method) usually cannot obtain a satisfied solution especially under the small sample situation. In this paper, the proposed method which incorporates the grey and possibilistic regression models formulates the novel portfolio selection model. In order to solve the multi-objective quadric programming problem, multi-objective evolution algorithms (MOEA) is employed. A numerical example is also illustrated to show the procedures of the proposed method. On the basis of the numerical results, we can conclude that the proposed method can provide the more flexible and accurate results. (c) 2004 Elsevier Inc. All rights reserved.
A study of boron diffusion from selectively grown epitaxial silicon-germanium into silicon during rapid thermal annealing
(2002)
Yang, TH
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Chang, EY
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Chen, KM
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Chien, CH
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Huang, HJ
Boron diffusion from selectively grown epitaxial Si1-xGex into Si during rapid thermal annealing (RTA) was investigated. Selective epitaxial growth (SEG) of in-situ boron-doped strained Si1-xGex epitaxial layers with different Ge percentages were selectively grown by ultra high vacuum chemical molecular epitaxy (UHVCME). The results show that the boron diffusion depth from SEG Si1-xGex into n-type Si depends on boron concentration, Ge profile in the SEG area, and the size of the SEG area. Higher boron concentrations in SEG Si1-xGex film increases the boron diffusion depth. However, the diffusion depth can be reduced by increasing Ge composition in SEG Si1-xGex. It was also found that the samples with graded Ge profiles have higher diffusion depths than those with uniform profiles. In addition, the boron diffusion depth increases with the size of the SEG Si1-xGex area. The strain in SEG Si1-xGex, the chemical potential of Ge in SEG Si1-xGex and the dislocations induced in the SEG Si1-xGex layers are the main reasons for the phenomena observed.
Analysis of low-frequency noise in boron-doped polycrystalline silicon-germanium resistors
(2002-09-30)
Chen, KM
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Huang, GW
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Chiu, DY
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Huang, HJ
;
Chang, CY
Low-frequency noise in boron-doped polycrystalline silicon-germanium (poly-Si1-xGex) resistors at various temperatures is studied. The poly-Si1-xGex films with 0%similar to36% Ge content were grown using ultrahigh vacuum chemical molecular epitaxy system. We find that the low-frequency noise in poly-Si1-xGex decreases with increasing Ge content, due to the lower potential barrier height of grain boundaries in higher Ge content samples. Moreover, the low-frequency noise decreases with increasing temperature. These results are well explained by the carrier mobility fluctuation model. (C) 2002 American Institute of Physics.
Bayesian classification for data from the same unknown class
(2002-04-01)
Huang, HJ
;
Hsu, CN
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資訊工程學系
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Department of Computer Science
In this paper, we address the problem of how to classify a set of query vectors that belong to the same unknown class. Sets of data known to be sampled from the same class are naturally available in many application domains, such as speaker recognition. We refer to these sets as homologous sets. We show how to take advantage of homologous sets in classification to obtain improved accuracy over classifying each query vector individually. Our method, called homologous naive Bayes (HNB), is based on the naive Bayes classifier, a simple algorithm shown to be effective in many application domains. HNB uses a modified classification procedure that classifies multiple instances as a single unit. Compared with a voting method and several other variants of naive Bayes classification, HNB significantly outperforms these methods in a variety of test data sets, even when the number of query vectors in the homologous sets is small. We also report a successful application of HNB to speaker recognition. Experimental results show that HNB can achieve classification accuracy comparable to the Gaussian mixture model (GMM), the most widely used speaker recognition approach, while using less time for both training and classification.
Deposition of polycrystalline Si and SiGe by ultra-high vacuum chemical molecular epitaxy
(2000-07-01)
Chen, KM
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Huang, HJ
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Chang, CY
;
Chen, LP
;
Huang, GW
The polycrystalline Si1-xGex (poly-Si1-xGex) films have better properties than poly-Si for device fabrications, such as lower proceeding temperature and process thermal budget. For these reasons, the poly-Si1-xGex films have been utilized for low-temperature thin film transistor fabrications and gate electrodes of metal-oxide-semiconductor transistors. In this work, disilane and germane were used to grow poly-Si1-xGex films at low temperature (<600 degrees C) by the cold-wall type ultrahigh vacuum chemical molecular epitaxy system. The poly-Si1-xGex films were deposited on oxide and nitride surfaces. The Ge fraction x was evaluated from x-ray diffraction and Auger electron spectroscopy. It is observed that the Ge fraction increases with the increase of the GeH4 flow rate. The result is only slightly related to the substrate type. The growth rate increases with the Ge fraction at lower values and then decreases with the Ge fraction in the higher composition range. This implies that the growth mechanism of poly-Si1-xGex films is different from that of epitaxial Si1-xGex on Si. The uniformity of poly-Si1-xGex films depends on the Ge fraction, and it is improved-by the addition of germanium. The result can be explained by the lower activation energy (<0.25 eV) of poly-Si(1-x)G(x), deposition as compared to that of poly-Si (similar to 2.1 eV). From the x-ray diffraction and atomic force microscopy analyses, the crystallinity and surface roughness of films are suitable for device fabrications. (C) 2000 American Vacuum Society. [S0734-2101(00)07704-6].
Electrical and compositional properties of co-silicided shallow p(+)-n junction using Si-capped/boron-doped Si1-xGex layer deposited by UHVCME
(2001-03-01)
Huang, HJ
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Chen, KM
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Chang, CY
;
Huang, TY
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電子工程學系及電子研究所
Co-silicided, strained boron-doped Si1-xGex p(+)/n junction with different Ge mole fractions deposited by ultrahigh vacuum chemical molecular epitaxy (UHVCME), suitable for raised source/drain metal oxide semiconductor field effect transistor applications, is studied. The electrical and compositional characteristics are presented. By using a Co/Si-cap/graded Si1-xGex structure, optimum forward and reverse diode characteristics with a near perfect forward ideality factor (i.e., <1.01) can be obtained for the p(+)-n junction. Thr low area leakage current extracted from Si-capped samples confirms that serious lattice misfit problems during silicidation, typical of Co/pure Si1-xGex samples, is largely eliminated by Si capping. In addition, the specific contact resistance is found to decrease as Ge mole fraction increases, and would be even lower if Si capping is used for silicidation. Finally, the composition of Co/Si1-xGex and Co/Si-cap/Si1-xGex interfacial reaction is studied by high-resolution X-ray spectra. Our results show that even after a second anneal at 850C, very little lattice distortion is discovered. Five harmonic peaks still remain even after a second anneal at 850 degreesC. Transmission electron micrograph also exhibits good uniformity and interface quality. (C) 2001 The Electrochemical Society. All rights reserved.
Electrical properties of shallow p(+)-n junction using boron-doped Si1-xGex layer deposited by ultrahigh vacuum chemical molecular epitaxy
(2001-05-01)
Huang, HJ
;
Chen, KM
;
Chang, CY
;
Chao, TS
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Huang, TY
Strained boron-doped Si1-xGex layers with different Ge mole fractions were selectively deposited by ultrahigh vacuum chemical molecular epitaxy to form shallow p(+)-n junction suitable for raised source/drain metal-oxide-semiconductor field effect transistor applications. Detailed electrical characterizations were performed. Our results show that the reverse leakage current could be optimized by a rapid thermal annealing at 950 degreesC for 20 s, and a near perfect forward ideality factor (i.e., <1.01) is obtained for the p(+)-n Si1-xGex/Si junction. By analyzing the periphery and area leakage current components of p(+)-n Si1-xGex/Si junctions with various perimeter lengths and areas, the degree of misfit dislocations and undercut effect were studied. The specific contact resistance was found to decrease as Ge mole fraction increases. Junction depth measurements also show that the junction depth decreases monotonically with increasing Ge mole fraction. The reduced B diffusion constant is attributed to the increasing Ge gradient in the transition region. (C) 2001 American Institute of Physics.
Folded quarter-wave resonator filters with Chebyshev, flat group delay, or quasi-elliptical function response
(2002)
Chang, CY
;
Chen, CC
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Huang, HJ
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電信工程研究所
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Institute of Communications Engineering
This paper presents the design and realization of a new class of miniaturized microstrip filters using folded quarter-wave resonators. Various kinds of filter response are realized by proper arrangement of the resonator. The design rules for cross-coupled filter with quasi-elliptical function and flat group delay response are provided. The measured results are matched well with the theoretical prediction.
Implications of the Dirichlet assumption for discretization of continuous variables in naive Bayesian classifiers
(2003-12-01)
Hsu, CN
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Huang, HJ
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Wong, TT
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資訊工程學系
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Department of Computer Science
In a naive Bayesian classifier, discrete variables as well as discretized continuous variables are assumed to have Dirichlet priors. This paper describes the implications and applications of this model selection choice. We start by reviewing key properties of Dirichlet distributions. Among these properties, the most important one is "perfect aggregation," which allows us to explain why discretization works for a naive Bayesian classifier. Since perfect aggregation holds for Dirichlets, we can explain that in general, discretization can outperform parameter estimation assuming a normal distribution. In addition, we can explain why a wide variety of well-known discretization methods, such as entropy-based, ten-bin, and bin-log l, can perform well with insignificant difference. We designed experiments to verify our explanation using synthesized and real data sets and showed that in addition to well-known methods, a wide variety of discretization methods all perform similarly. Our analysis leads to a lazy discretization method, which discretizes continuous variables according to test data. The Dirichlet assumption implies that lazy methods can perform as well as eager discretization methods. We empirically confirmed this implication and extended the lazy method to classify set-valued and multi-interval data with a naive Bayesian classifier.
Improved electrical properties of shallow p(+)-n junction using selectively grown graded Si1-xGex epitaxial structure
(2000-12-01)
Huang, HJ
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Chen, KM
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Chang, CY
;
Huang, TY
;
Chen, LP
A strained boron-doped graded Si1-xGex structure consisting of layered Si1-xGex with increasing Ge mole fractions was studied as the solid diffusion source for forming a p(+)-n junction suitable for raised source/drain metal oxide semiconductor field effect transistor (MOSFET) application. The in situ doped graded Si1-xGex structure was selectively epitaxially grown (SEG) on the active region using ultrahigh vacuum chemical molecular epitaxy (UHVCME). Improved electrical characteristics, not possible with conventional uniform SEG Si1-xGex junction, are achieved with the graded SEG Si1-xGex junction. For the conventional uniform Si1-xGex junction, while a high Ge composition is necessary for reducing the specific contact resistance and the sheet resistance, such a high Ge composition, also results in a degraded ideality factor and a leaky junction. In contrast, a near-perfect SiGe/Si interface property is demonstrated with the graded Si1-xGex structure. Optimum specific contact resistance and the sheet resistance can be obtained by the graded Si1-xGex structure without suffering degraded junction leakage and ideality factor. These results indicate that the degree of misfit dislocation and the undesirable undercut effects could be effectively reduced by using the graded structure with its lower Ge composition close to the silicon substrate, while a low sheet resistance and specific contact resistance is preserved with its higher Ge composition at the top of the layered structure. (C) 2000 The Electrochemical Society. S1099-0062(00)08-111-6. All rights reserved.
Improved low temperature characteristics of p-channel MOSFETs with Si1-xGex raised source and drain
(2001-08-01)
Huang, HJ
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Chen, KM
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Huang, TY
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Chao, TS
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Huang, GW
P-channel metal-oxide-semiconductor field-effect transistors with Si1-xGex raised source and drain (RSD) have been fabricated and further studied for low temperature applications. The Si1-xGex RSD layer was selectively grown by ANELVA. SRE-612 ultra-high vacuum chemical vapor deposition (UHVCVD) system, Compared to devices with conventional Si RSD, improved transconductance and specific contact resistance were obtained, and these improvements become even more dramatic with reducing channel length, Well-behaved short channel characteristics with reduced drain-induced barrier lowering (DIBL) and off-state leakage current are demonstrated on devices with 100 nm Si1-xGex RSD, due to the resultant shallow junction and less implantation damage. Moreover, temperature measurements reveal that Si1-xGex RSD devices show more dramatic improvement in device performance at low temperature (-50 degreesC) operation, which can be ascribed to the higher temperature sensitivity of the Si1-xGex sheet resistance.
Reduction of source/drain series resistance and its impact on device performance for PMOS transistors with raised Si1-xGex source/drain
(2000-09-01)
Huang, HJ
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Chen, KM
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Chang, CY
;
Chen, LP
;
Huang, GW
P-channel MOS transistors with raised Si1-xGex and Si source/drain (S/D) structure selectively grown by ultra high vacuum chemical vapor deposition (UHVCVD) were fabricated for the first time. The impacts of Si1-xGex and Si epitaxial S/D layer on SID series resistance and drain current of p-channel transistors were studied. Our result show that the new device with Si1-xGex raised S/D layer depicts only half the value of the specific contact resistivity and S/D series resistance (R-SD), compared to the device with Si raised S/D layer. The improvement is even more dramatic, when comparing to the conventional device without any raised Sin layer i.e., R-SD of the new device with Si1-xGex raised S/D is only about one fourth the value of the conventional device. Moreover, the device with raised SiGe S/D structure produces a 29% improvement in transconductance (g(m)) at an effective channel length of 0.16 mu m, These performance improvements, together with several inherent advantages such as self-aligned selective epitaxial growth (SEG) nature and the resultant T-shaped gate structure, make the new device with raised Si1-xGex S/D structure very attractive for future sub-0.1 mu m p-channel MOS transistors.
Study of boron effects on the reaction of Co and Si1-xGex at various temperatures
(2000-07-01)
Huang, HJ
;
Chen, KM
;
Chang, CY
;
Huang, TY
;
Chang, TC
The effects of boron on Co and Si1-xGex interfacial reaction were studied. Undoped and ill situ boron-doped strained Si0.91Ge0.09 and Si0.86Ge0.14 layers prepared at 550 degrees C by an ultrahigh vacuum chemical vapor deposition system were subjected to Co silicidation at various rapid thermal annealing (RTA) temperatures ranging from 500 to 1000 degrees C. The resulting films were characterized by a sheet resistance measurement, Auger electron spectroscopy, x-ray diffractometry (XRD), high resolution x-ray diffractometry, secondary ion mass spectroscopy, scanning electron microscopy, and transmission electron microscopy. Seen from XRD spectroscopy, a Co(Si1-yGey) cubic structure was formed with RTAs ranging from 500 to 700 degrees C. For boron-doped samples, the CoGe fraction in Co(Si1-yGey) was less than that in undoped samples, indicating that baron atoms retarded the incorporation of Ge into the Co(Si1-yGey) ternary phase. It also led to a large Ge pileup at the interface between the Co-rich and silicidation regions. On the other hand, from the high resolution x-ray spectra, the presence of boron led to less relaxation of the strained Si1-xGex lattice. It is the first time that small boron atoms inhibiting the relaxation of the Si1-xGex layer during silicidation was observed. Furthermore, from the sheet resistance measurement, the formation of CoSi2 was found to be slightly retarded in boron-doped samples, due probably to the decrease of Co or Si diffusivities as a result of boron accumulation at the Co/SiGe reaction interface. At temperatures above 800 degrees C, CoSi2 formed and Ge segregated to the silicide boundaries and the upper reaction region was discovered. These phenomena caused by B dopants are explained in detail. (C) 2000 American Vacuum Society. [S0734-2101(00)04604-2].
Study on Ge/Si ratio, silicidation, and strain relaxation of high temperature sputtered Co/Si1-xGex structures
(2000-08-15)
Huang, HJ
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Chen, KM
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Chang, CY
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Huang, TY
;
Chen, LP
As the transistors continue to scale down, the characteristics of high-temperature-sputtered Co/Si1-xGex junction have received lots of attention because of its potential applications to heterojunction bipolar transistors. In this study, we have fabricated Co/Si1-xGex junction using room-temperature and high-temperature (i.e., at 450 degrees C) sputtered Co on top of strained Si0.86Ge0.14 and Si0.91Ge0.09 layers prepared by ultrahigh vacuum chemical molecular epitaxy. The relative composition of Ge in Ge-rich Si1-zGez precipitate and the solid solution of ternary phase silicide of Co-Si-Ge system were compared between room-temperature and high-temperature sputtered samples. We found that the high-temperature-sputtered samples are more effective in inhibiting lattice relaxation, which would be beneficial for manufacturing metal silicide/Si1-xGex structure devices. Mechanisms were proposed to explain the large difference between the room-temperature and high-temperature sputtered samples. It is believed that the mixed Co-Si-Ge solution on high-temperature-sputtered samples is responsible for the different silicidation behaviors. (C) 2000 American Institute of Physics. [S0021-8979(00)02616-5].
The ANNIGMA-wrapper approach to fast feature selection for neural nets
(2002-04-01)
Hsu, CN
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Huang, HJ
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Schuschel, D
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資訊工程學系
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Department of Computer Science
This paper presents a novel feature selection approach for backprop neural networks (NNs). Previously, a feature selection technique known as the wrapper model was shown effective for decision trees induction. However, it is prohibitively expensive when applied to real-world neural net training characterized by large volumes of data and many feature choices. Our approach incorporates a weight analysis-based heuristic called artificial neural net input gain measurement approximation (ANNIGMA) to direct the search in the wrapper model and allows effective feature selection feasible for neural net applications. Experimental results on standard datasets show that this approach can efficiently reduce the number of features while maintaining or even improving the accuracy. We also report two successful applications of our approach in the helicopter maintenance applications.
The reaction of Co and Si1-xGex for MOSFET with poly-Si1-xGex gate
(2001-03-01)
Chen, KM
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Huang, HJ
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Chang, CY
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Huang, TY
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Huang, GW
The effects of Ge on the interfacial reaction between Co and poly-Si1-xGex materials were studied. Poly-Si1-xGex layers prepared at 580 degreesC by ultra-high vacuum chemical molecular epitaxy (UHVCME) system were subjected to Co silicidation at various rapid thermal annealing (RTA) temperatures ranging from 500 to 900 degreesC. From X-ray diffractometry (XRD), Co(Si1-xGex) cubic structure was formed with RTA temperature ranging from 500 to 800 degreesC for x = 0.09, while CoSi2 was formed at 900 degreesC. However, for x = 0.21, Co(Si1-yGey) persisted even after 900 degreesC RTA annealing, and CoSi2 was not found. These results indicate that Ge atoms retard the formation of CoSi2, As a result, the RTA temperature needed to obtain low sheet resistance has to be increased with increasing Ge content. Finally, p-channel metal-oxide-semiconductor (MOS) transistors with poly-Si1-xGex-gate have been successfully integrated with Co salicidation process. (C) 2001 Elsevier Science B.V. All rights reserved.