Browsing by Issue Date, starting with "1994-09-01"

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EFFECTS OF SIH4, GEH4, AND B2H6 ON THE NUCLEATION AND DEPOSITION OF POLYCRYSTALLINE SI1-XGEX FILMS
(1994-09-01)
LIN, HC
;
CHANG, CY
;
CHEN, WH
;
TSAI, WC
;
CHANG, TC
In this study, the effects of different reactants, namely, SiH4, GeH4 and B2H6, on the nucleation and deposition of polycrystalline silicon-germanium (poly-Si1-xGe(x)) films on oxide surface in an ultrahigh vacuum chemical vapor deposition reactor were explored. The results show that the addition of GeH4 tends to retard the nucleation process of poly films while B2H6 is preferential for adsorbing on the oxide surface. These effects lead to different incubation duration depending on the kind of reactants used. On the deposition of poly-Si1-xGe(x) films, it is observed that the Ge incorporation is only slightly related to the substrate type, but the deposition mode of poly-Si1-xGe(x) films is much different from that of epitaxial growth on Si(100). The incorporation of Ge atoms also overcomes the anomalous doping effect encountered in heavily boron-doped poly-Si films and allows extremely low resistivity (below 2 mOMEGA-cm) poly films to be obtained at low temperatures (less-than-or-equal-to550-degrees-C).
EFFECT OF SOAKING TIME ON THE TEMPERATURE-COEFFICIENT OF RESISTIVITY OF SEMICONDUCTING BARIUM-TITANATE PTCR CERAMICS
(1994-09-01)
LU, YY
;
LAI, CH
;
TSENG, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The influence of soaking time at 1200 degrees C on the temperature coefficient of resistivity (TCR) of semiconducting barium titanate ceramics has been investigated. It is found that soaking duration has influence on the room-temperature resistivity, the maximum resistivity, the temperature (T-max) at which the maximum resistivity appears, and TCR of the positive temperature coefficient of resistivity (PTCR) ceramics. The increased room-temperature resistivity with the increase of soaking time is contributed mainly by the increase of grain boundary resistivity examined by the complex-plane impedance method. The obtained surface acceptor density (N-s) by capacitance-voltage measurement is found to increase with the soaking duration. The higher N-s contributes to higher built-in potential and results in lower T-max and higher maximum resistivity. Therefore, the increased surface acceptor density from increasing the soaking time at 1200 degrees C increases the temperature coefficient of resistivity of PTCR ceramics.
IMPEDANCE MATRICES FOR 2 AXIAL SYMMETRICAL FOUNDATIONS ON LAYERED MEDIUM
(1994-09-01)
LIOU, GS
;
交大名義發表
;
土木工程學系
;
National Chiao Tung University
;
Department of Civil Engineering
An attempt is made to generate impedance matrices for two independent axial symmetric foundations on an elastic layered medium. The analytic solution of three dimensional wave equations for a layered medium with the prescribed traction due to vibration of one axial symmetric foundation can be found using the technique developed in Refs. [3,4,5]. Two analytic solutions for two prescribed tractions due to the vibrations of two axial symmetric foundations are found separately. The principle of superposition is then used to obtain the final solution. The interaction stresses at the interfaces between the foundations and layered soil medium are assumed to be piecewise linear in r-directions of both cylindrical coordinates for two axial symmetric foundations. Then, the variational principle and reciprocal theorem are employed to generate the impedance matrices for both foundations. Some numerical results of impedance matrices for the interaction of two closely spaced circular foundations are presented, in order to show the effectiveness and efficiency of the presented method and the effect of layered stratum on the vibrations of two independent foundations. Discussion and conclusions are made.
A HARDWARE IMPLEMENTABLE RECEDING HORIZON CONTROLLER FOR CONSTRAINED NONLINEAR-SYSTEMS
(1994-09-01)
LIN, SY
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
;
Institute of Electrical and Control Engineering
We present a two-phase parallel computing method for obtaining an implementable receding horizon control solution for constrained nonlinear systems. The phase 1 method solves a feasibility problem to find an approximate open-loop admissible control and horizon pair. The phase 2 method successively improves the admissible control to obtain an implementable open-loop receding horizon control solution. We briefly sketch an approach to realizing this two-phase method using VLSI array processors. Solution times for simulation examples estimated on the basis of current VLSI technology confirm that our controller is well suited to the stabilization of real-time processing, fast, constrained nonlinear systems.
EFFECTS OF HOT-CARRIER-INDUCED INTERFACE STATE GENERATION IN SUBMICRON LDD MOSFETS
(1994-09-01)
WANG, TH
;
HUANG, CM
;
CHOU, PC
;
CHUNG, SSS
;
CHANG, TE
A two-dimensional numerical simulation including a new interface state generation model has been developed to study the performance variation of a LDD MOSFET after a dc voltage stress. The spatial distribution of hot carrier induced interface states is calculated with a breaking silicon-hydrogen bond model. Mobility degradation and reduction of conduction charge due to interface traps are considered. A 0.6 mum LDD MOSFET was fabricated. The drain current degradation and the substrate current variation after a stress were characterized to compare the simulation. A reduction of the substrate current at V(g) congruent-to 0.5 V(d) in a stressed device was observed from both the measurement and the simulation. Our study reveals that the reduction is attributed to a distance between a maximum channel electric field and generated interface states.
DIFFERENCE AND SIMILARITY MODELS OF 2 IDEMPOTENT OPERATORS
(1994-09-01)
WANG, JH
;
WU, PY
;
應用數學系
;
Department of Applied Mathematics
In a recent work, Hartwig and Putcha obtained a complete characterization of those finite matrices which can be expressed as the difference of two idempotents. Extending this result to operators on a possibly infinite-dimensional Hilbert space seems more difficult. In this paper, we initiate its study and obtain, among other things, (1) that not every nilpotent operator is the difference of two idempotents, (2) that if T is the difference of two idempotents, then the spectra of T and -T differ at most by the two points +/-1, and (3) a characterization of differences of two idempotents among normal operators. In the second part of the paper, we develop some similarity-invariant models of two idempotents. These are analogous to the known unitary-equivalence-invariant models for two orthogonal projections.
GLOBAL OPTIMIZATION FOR MIXED 0-1 PROGRAMS WITH CONVEX OR SEPARABLE CONTINUOUS-FUNCTIONS
(1994-09-01)
LI, HL
;
交大名義發表
;
資訊管理與財務金融系註：原資管所+財金所
;
National Chiao Tung University
;
Department of Information Management and Finance
This paper proposes a global approach for solving mixed 0-1 programming problems containing convex or separable continuous functions. Given a mixed 0-1 polynomial term z = x1x2...x(n)g(Y) where x1, x2,..., x(n) are 0-1 integer variables and g(Y) is a convex or a separable continuous function, we can transform z into a set of inequalities where x1, x2,..., x(n) and g(Y) are separated from each other. Based on this transformation, the original mixed 0-1 program can then be solved by a branch-and-bound method to obtain a global optimum.
POOL - AN UNBOUNDED ARRAY
(1994-09-01)
WU, PC
;
WANG, FJ
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Many collection objects, e.g., stack, can be implemented with tabular representation (an array). Such an implementation provides fast index and saves space on linked structures. However, its space is bounded at creation time. This note presents a hybrid data structure, called pool, which combines tabular and indexed data structures. A pool is a number of segments of contiguous memory space. It provides unbounded space. Its first segment is allocated initially. When more space is needed, a new segment is allocated in double size of previous segment. All segments allocated can be accessed via an index table. The size of index table is log n, where n is the number of elements. A pool can provide index operation in O(log n) and iterations almost as fast as tabular implementation.
EFFECTS OF VACANCIES ON THE ELECTRICAL CHARACTERISTICS OF METAL GAAS SCHOTTKY CONTACTS A QUANTITATIVE MODEL
(1994-09-01)
SZE, JJ
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An analytical method, proceeding by solving the Poisson equations both in the metal and in the GaAs substrate, is proposed to study the effects of the vacancies on the electrical characteristics of metal/GaAs contacts. A quantitative model used to calculate the effective charges contributed by the vacancies is developed here for the first time. From this analysis, it is found that the phenomenon of the Fermi level pinning in metal/GaAs contacts can be explained by the existence of vacancies at the metal/GaAs interface. Because of the amphoteric property of the vacancies in GaAs, the Fermi level is pinned at a level, called the ''neutral level'' of the vacancy, at which the effective charge introduced by the vacancies is zero. The change of the Fermi level pinning positions observed in previous experimental results for p and n GaAs can be ascribed to the change of vacancy types due to the nonstoichiometry in the GaAs substrate.
GLOBAL SHAPE INFORMATION MODELING AND CLASSIFICATION OF 2D WORKPIECES
(1994-09-01)
WU, MC
;
CHEN, JR
;
JEN, SR
;
交大名義發表
;
工業工程與管理學系
This paper presents a representation scheme for modelling the global shape information of 2D workpieces and uses this representation scheme to classify workpieces. The global shape information of a workpiece could be seen as its topological structure. Retrieving workpieces with similar global shape would facilitate some design and manufacturing activities. To derive the proposed representation scheme, a 2D workpiece first has to be approximately enclosed by a rectilinear polygon. Then, the simplified skeleton of the rectilinear polygon, a tree structure consisting of a set of line segments, is derived. The line segments on the simplified skeleton involve two types: real links and virtual links. In this paper, we prove that each real link models a rectangular region, and the union of the modelling regions of all real links is equal to the region enclosed by the rectilinear polygon. Briefly, the simplified skeleton of a rectilinear polygon denotes a global decomposition of the polygon, and is topologically similar to the polygon. On the basis of simplified skeletons, a neural network approach is developed for classifying 2D workpieces.
ENHANCEMENT OF THE STARK-EFFECT IN ALINAS/GAINAS COUPLED QUANTUM-WELLS AND THEIR APPLICATIONS TO TUNABLE MIDINFRARED PHOTODETECTORS
(1994-09-01)
HUANG, YM
;
LIEN, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A tunable midinfrared photodetector using 1 --> 4 intersubband Stark shift in the four-level AlInAs/GaInAs coupled quantum wells (CQWs) is proposed. The operation of this device is based on the infrared absorption by the electrons in the ground state transited from the ground-state subband E1 of the CQWs to the third-excited-state subband E4. A large variation of eigenenergy spacing DELTAE41 between E1 and E4 under an applied electric field can be achieved for the proposed AlInAs/GaInAs CQW system. Since the infrared radiation is absorbed via the intersubband resonance absorption (homegaBAR = E4-E1), the detected infrared wavelength can be tuned by the spacing DELTAE41 which can be adjusted by an applied electric field. The tunability of these AlInAs/GaInAs CQWs have been studied theoretically. Based on theoretical calculations, tuning ranges from 3 to 3.9 and 2.9 to 4.2 mum are predicted for the proposed asymmetric CQW structure and compositionally asymmetric COW structure, respectively. This tuning capability is achieved by varying the applied electric field in the 90 to -90 kV/cm range.
ANALYSIS OF SURFACE-STATE EFFECT ON GATE LAG PHENOMENA IN GAAS-MESFETS
(1994-09-01)
LO, SH
;
LEE, CP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A two-dimensional transient simulation of the gate lag phenomenon in GaAs MESFET's has been performed. Our results show that the charge exchanges in the population of the surface states at the ungated access region of FET's are responsible for this slow transient phenomenon. The measured ''hole-trap-like'' DLTS signal is directly related to the re-emission of the holes, trapped during the filling pulse. Higher gate pulse can cause more serious lag phenomenon due to larger modulation of surface charge density. Devices with shorter N+-gate spacing and lower surface state densities are shown to have less gate lag effect.
UNTITLED
(1994-09-01)
HUANG, TL
;
交大名義發表
;
National Chiao Tung University
PARAMETRIC MULTIPLE EIGENVALUE SHIFTING WITH MINIMUM EIGEN-VALUE SENSITIVITY VIA STATE-FEEDBACK BASED ON BLOCK SCHUR FORM
(1994-09-01)
LIN, JJ
;
WU, YC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Based on the block Schur form of an open-loop system matrix, a new sequential design procedure is proposed for characterizing an explicit parametric class of linear state-feedback controllers for the open-loop system, which will shift an arbitrary prescribed spectrum of distinct self-conjugate multiple eigenvalues to the closed-loop system. We also consider the problem of minimizing the sensitivity of the shifted closed-loop multiple eigenvalues with respect to parameter variations in all elements of the closed-loop plant matrix. An insightful parameterization of the desirable closed-loop multiple eigenvalue sensitivity is provided through the explicit parametric class of linear state-feedback controllers. Based on this parameterization, a least square method for designing a state-feedback gain matrix which shifts a desirable set of distinct closed-loop multiple eigenvalues, such that these multiple eigenvalues have minimum sensitivity to perturbation in the closed-loop plant matrix, is presented. A numerical example is worked out to illustrate the design procedures.
IDENTIFICATION OF A CLASS OF NONLINEAR DETERMINISTIC SYSTEMS WITH APPLICATION TO MANIPULATORS
(1994-09-01)
LIN, SK
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
;
Institute of Electrical and Control Engineering
This note presents a recursive identification method to estimate the minimal parameters of a class of nonlinear deterministic system. The result can be applied to a manipulator with unknown torque constants. A procedure to identify the torque constants, the friction, and the gravity parameters at the same time is then proposed. This is worthwhile since the PD feedback control with the gravity and friction compensation ensures a zero steady-state response for the set-point control. A theory addresses the minimal parameters composed of the three groups of parameters. The identification procedure for the minimal parameters is conducted by moving one joint with a constant velocity at a time. The persistently exciting trajectories for the identification are also suggested. The experiment on the PUMA 560 illustrates the identification method.
ELECTROLUMINESCENCE OF A-SIC-H P-I-N THIN-FILM LIGHT-EMITTING-DIODES WITH QUANTUM-WELL-INJECTION STRUCTURES
(1994-09-01)
JEN, TS
;
SHIN, NF
;
TSAY, WC
;
CHEN, JY
;
NING, SL
In order to improve the electroluminescence (EL) characteristics of hydrogenated amorphous silicon carbide (a-SiC:H) p-i-n thin-film light-emitting diodes (TFLEDs), the quantum-well-injection (QWI) structures have been incorporated into their intrinsic (i-) layer. Two types of TFLED were fabricated to study the effect of the incorporated QWI structures on their EL characteristics: the device I contains a step-gap QWI structure of barrier (15 angstrom)/well (45 angstrom)/barrier (15 angstrom) inserted at both the p-i and i-n interfaces, and the device Il has only one graded-gap QWI structure of barrier (10 angstrom)/well (10 angstrom)/barrier (10 angstrom) inserted at the p-i interface. The obtained brightness of device I was about 10 cd/m2 at an injection current density of 1 A/cm2. The emission light of device I was yellow-like as detected by human eyes. Whereas, for device II, the brightness was about 256 cd/m2 at 800 mA/cm2 and an orange light emission was observed.
SIMPLIFYING SEQUENTIAL-CIRCUIT TEST-GENERATION
(1994-09-01)
SHEU, ML
;
LEE, CL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Design for testability reduces testing costs for sequential circuits. The authors present a parity checker DFT scheme they have incorporated into a finite-state machine synthesis system. Generating tests for circuits synthesized according to this scheme becomes extremely simple. The derived test sequence very efficiently detects faults.
A SILICIDATION-INDUCED PROCESS CONSIDERATION FOR FORMING SCALE-DOWN SILICIDED JUNCTION
(1994-09-01)
CHENG, HC
;
JUANG, MH
;
LIN, CT
;
HUANG, LM
;
電子工程學系及電子研究所
A process consideration for forming silicided shallow junctions, arising from silicidation process, has been discussed. The CoSi2 shallow p+n junctions formed by various schemes are characterized. The scheme that implants BF2+ ions into thin Co films on Si substrates and subsequent silicidation yields good junctions, but the problems about the dopant drive-in and knock-on of metal deeply degrade this scheme. In the regime that implants the dopant into Si and then Co deposition, however, a large perimeter leakage of 0.1 nA/cm is caused. Generation current, associated with a defect-enhanced diffusion of Co in Si during silicidation, dominates the leakage. A high-temperature pre-activation prior to Co deposition reduces the perimeter leakage to 0.038 nA/cm, but which deepens the junctions.
INCREASING CHARACTER-RECOGNITION ACCURACY BY DETECTION AND CORRECTION OF ERRONEOUSLY IDENTIFIED CHARACTERS
(1994-09-01)
TUNG, CH
;
LEE, HJ
;
資訊工程學系
;
Department of Computer Science
This paper presents a general approach to increasing character recognition accuracy by detection and correction of erroneously identified characters. A high-accuracy two-stage recognition system for recognizing handwritten Chinese text with 5401 categories is demonstrated. In the first stage of the system, two matching modules are applied to recognize an input character simultaneously. The first matching module uses a direction feature and the second uses a generalized feature. A character is rejected at the first stage when the matching results of the two modules are not the same. Because our first stage recognizes most of the input characters correctly and outputs a small number of candidates for each rejected character, a bigram Markov language model in the second stage can choose a candidate with high recognition rate for each rejected character according to contextual information. Experiments are performed on sentences consisting of characters extracted from the CCL/HCCR1 handwritten Chinese character database. In the first stage, the rejection rate for the input characters is 13% and the recognition rate for the accepted characters is 95.9%. In the second stage, the recognition rate for the characters rejected by the first stage is 91.2%. Thus, the overall recognition rate for the input handwritten text is 95.9% x 0.87 + 91.2% x 0.13 (= 95.2%)
ENHANCEMENT OF THE STARK-EFFECT IN ALINAS/GAINAS COUPLED QUANTUM-WELLS AND THEIR APPLICATIONS TO TUNABLE MIDINFRARED PHOTODETECTORS
(1994-09-01)
HUANG, YM
;
LIEN, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A tunable midinfrared photodetector using 1 --> 4 intersubband Stark shift in the four-level AlInAs/GaInAs coupled quantum wells (CQWs) is proposed. The operation of this device is based on the infrared absorption by the electrons in the ground state transited from the ground-state subband E1 of the CQWs to the third-excited-state subband E4. A large variation of eigenenergy spacing DELTAE41 between E1 and E4 under an applied electric field can be achieved for the proposed AlInAs/GaInAs CQW system. Since the infrared radiation is absorbed via the intersubband resonance absorption (homegaBAR = E4-E1), the detected infrared wavelength can be tuned by the spacing DELTAE41 which can be adjusted by an applied electric field. The tunability of these AlInAs/GaInAs CQWs have been studied theoretically. Based on theoretical calculations, tuning ranges from 3 to 3.9 and 2.9 to 4.2 mum are predicted for the proposed asymmetric CQW structure and compositionally asymmetric COW structure, respectively. This tuning capability is achieved by varying the applied electric field in the 90 to -90 kV/cm range.