Browsing by Issue Date, starting with "1996-01-08"

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A bilayer Ti/Ag ohmic contact for highly doped n-type GaN films
(1996-01-08)
Guo, JD
;
Lin, CI
;
Feng, MS
;
Pan, FM
;
Chi, GC
Ohmic contacts with low resistance are fabricated on n-type GaN films using Ti/Ag bilayer metallization. The GaN films are grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) with Si as the dopant. Ohmic characteristics are studied for films with carrier concentration range from 1.5 x 10(17) to 1.7 x 10(19) cm(-3). The lowest value for the specific contact resistivity of 6.5 x 10(-5) Ohm cm(2) is obtained without annealing. The barrier height of Ti on GaN is calculated to be 0.067 eV. (C) 1996 American Institute of Physics.
Studies on damage removing efficiency of B-11(+) and BF2+ implanted Si0.84Ge0.16 epilayers by rapid thermal annealing
(1996-01-08)
Chen, LP
;
Chou, TC
;
Chien, CH
;
Chang, CY
;
電控工程研究所
High quality metastable pseudomorphic Si1-xGex epilayers were grown by ultrahigh vacuum chemical vapor deposition using Si2H6 and GeH4. These epilayers were implanted with 40 keV B-11(+) and 100 keV BF2+ ions at a dose of 1 x 10(15) ions/cm(2) and then annealed by rapid thermal annealing (RTA) processes at temperatures of 600, 650, 700, and 750 degrees C for 30 s duration. Double-crystal x-ray diffractometry was used to evaluate the level of the implant-induced damage and the damage removing efficiency of both ion implanted samples at different RTA conditions. The results show that the RTA process is more effective at removing damage from B-11(+) implanted samples than from those implanted with BF2+. (C) 1996 American Institute of Physics.
Free-carrier absorption in n-type gallium arsenide films for polar optical phonon scattering
(1996-01-15)
Wu, CC
;
Lin, CJ
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應用數學系
;
電控工程研究所
;
Department of Applied Mathematics
The free-carrier absorption in n-type GaAs films has been investigated for quantum well structures fabricated from III-V semiconducting materials where polar optical phonon scattering is predominant. Attention is given mainly to the case where the electromagnetic radiation is polarized in the layer plane, and the processes involving both emission and absorption of polar optical phonons. The energy band of electrons in semiconductors is assumed to be nonparabolic. Results are shown that the free-carrier absorption coefficient in n-type GaAs films depends upon the photon frequency, the width of the quantum wells, and temperature. However, in the small quantum well region such as the width of quantum wells d<30 Angstrom, the free-carrier absorption coefficient will be independent of temperature. Moreover, the free-carrier absorption coefficient oscillates with the width of quantum wells for larger quantum wells. (C) 1996 American Institute of Physics.
Epoxy-polycarbonate blends catalyzed by a tertiary amine .1. Mechanism of transesterification and cyclization
(1996-01-15)
Li, MS
;
Ma, CCM
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Chen, JL
;
Lin, ML
;
Chang, FC
In the Bisphenol A base polycarbonate-Bisphenol A base epoxy blend system, the carbonate group can react with epoxide in the presence of a tertiary amine. The transesterification reactions convert the original aromatic/aromatic carbonate of PC to aromatic/aliphatic and aliphatic/aliphatic carbonates. IR spectroscopy shows an unknown major structure formed during the later stages of the transesterification reaction. The unknown structure was investigated by a model reaction using diphenyl carbonate and phenyl glycidyl ether leading to the formation of 4-(phenoxymethyl)-1,3-dioxolan-2-one (PMD), which has been identified by IR, UV, H-1 NMR, C-13 NMR, and mass spectroscopy. The mechanism of forming the cyclic carbonate is proposed to proceed through a zwitterion and a nucleophile attack of the aromatic/aliphatic or the aliphatic/aliphatic carbonate group.
The partial gossiping problem
(1996-01-15)
Chang, GJ
;
Tsay, YJ
;
應用數學系
;
Department of Applied Mathematics
This paper studies the following variation of the gossiping problem. Suppose there are n persons, each of whom knows a message. A pair of persons can pass all messages they have by making a telephone call. The partial gossiping problem is to determine the minimum number of calls needed for each person to know at least k messages. This paper gives a complete solution to this problem.
Compositional disordering of InGaAs/GaAs heterostructures by low-temperature-grown GaAs layers
(1996-01-15)
Tsang, JS
;
Lee, CP
;
Lee, SH
;
Tsai, KL
;
Tsai, CM
Compositional disordering of InGaAs/GaAs superlattices using a low-temperature-grown GaAs cap layer (LT-GaAs) by molecular beam epitaxy has been studied. The disordering of the superlattice was verified by photoluminescence and double-crystal x-ray rocking curve measurements. The Ga-vacancy-enhanced interdiffusion due to the presence of LT-GaAs was found to be the disordering mechanism. Diffusion equations and the Schrodinger's equation were solved numerically to obtain the composition profile and the transition energies in the disordered quantum well, respectively. The simulated energy shifts for samples under different annealing conditions agreed very well with the experimental results. The calculated effective diffusivity for the In-Ga interdiffusion has an activation energy of 1.63 eV, which is smaller than the activation energy 1.93 eV, for intrinsic interdiffusion. The diffusivity for the enhanced In-Ga interdiffusion due to the presence of LT-GaAs is about two orders of magnitude larger than the intrinsic In-Ga diffusivity. (C) 1996 American Institute of Physics.
Formation of mononuclear nitrido complexes of chromium(VI) and molybdenum(VI); Syntheses and X-ray crystal structures of N Cr(OBu(t))(3) and N Mo(OSiMe(3))(3)(py)
(1996-01-21)
Chiu, HT
;
Chen, YP
;
Chuang, SH
;
Jen, JS
;
Lee, GH
Mononuclear nitrido complexes of Cr and Mo, N=Cr(OBu(t))(3) and N=Mo(OSiMe(3))(3)(py), are synthesized; the chromium complex has an idealized C-3v symmetry while the molybdenum complex has a distorted square-pyramidal geometry with the nitrido ligand at apical position; the N-Cr distance is 1.538(5) Angstrom while the average N-Mo distance is 1.627 Angstrom.
Effect of rapid thermal annealing on the electrical and physical properties of metalorganic chemical-vapor-deposited TiN
(1996-01-29)
Sun, SC
;
Tsai, MH
;
奈米中心
;
Nano Facility Center
This work reports on the effect of postdeposition thermal treatment using rapid thermal annealing on the physical and electrical properties of metalorganic chemical-vapor-deposited (MOCVD) titanium nitride (TiN) thin films. When ammonia is used as the annealing ambient, the resistivity decreases with increasing annealing temperature. The resistivity of MOCVD TiN was reduced from 6000 to 320 mu Omega cm after 800 degrees C rapid thermal annealing in ammonia (RTN). Annealing in nitrogen ambient was found to be not nearly as effective as that in ammonia. The decrease in resistivity may be attributed to a reduction in the carbon and oxygen content, growth in grain size through polycrystalline recrystallization, as well as to an increase in film density. (C) 1995 American Institute of Physics.
Effect of thermal annealing on electrical conductivities in arsenic-ion-implanted GaAs
(1996-01-29)
Chen, WC
;
Chang, CS
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
The effect of thermal annealing on the electrical conductivities of arsenic-ion-implanted GaAs has been investigated by deep level transient spectroscopy and temperature-dependent conductance measurements. For the annealed films of arsenic-ion-implanted GaAs a band of deep-level defects with the activation energy of around 0.55 eV below the conduction band is found. The dense concentration of traps is able to reduce the carrier concentration from 3 X 10(18) to 2 X 10(17) cm(-3). The cross section of the deep level is calculated to be 1.5 X 10(-14) cm(2). The carrier-transport mechanisms of both as-implanted GaAs and postannealed GaAs are dominantly shown to be a separate hopping and active-type conduction. (C) 1996 American Institute of Physics.
An algorithm for inverting rational matrices
(1996-01-31)
Lin, CA
;
Yang, CW
;
Hsieh, TF
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交大名義發表
;
電控工程研究所
We propose an algorithm for computing the inverses of rational matrices and in particular the inverses of polynomial matrices. The algorithm is based on minimal state space realizations of proper rational matrices and the matrix inverse lemma and is implemented as a MATLAB function. Experiments show that the algorithm gives accurate results for typical rational matrices that arise in analysis and design of linear multivariable control systems. Illustrative examples are given.
A study on blends of liquid crystalline copolyesters with polycarbonate .2. Transesterification control
(1996-01-31)
Wei, KH
;
Su, KF
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交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
The inhibited and catalyzed ester exchange (transesterification) during melt blending of poly(bisphenol-A carbonate) (PC) and liquid crystalline poly(oxybenzoate-co-ethylene terephthalate) (POB-PET 40/60; P46) was investigated with differential scanning calorimetry. It was found that the ester exchange between P46 and PC was effectively inhibited for a 20% P46 blend at 240 degrees C, as further confirmed by nuclear magnetic spectroscopy. When the blending temperature and P46 concentration increased, only the transesterification between the PET segment in P46 and PC took place under inhibition. The morphology of the blends was analyzed with scanning electron microscopy and displayed a disconnected interface between P46 and PC under inhibition. Conversely, the transesterification took place between the POB segment in P46 and PC when a catalyst was added. (C) 1996 John Wiley & Sons, Inc.
Effect of oxygen concentration in the sputtering ambient on the microstructure, electrical and optical properties of radio-frequency magnetron-sputtered indium tin oxide films
(1996-02-01)
Wu, WF
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Indium tin oxide (ITO) films have been prepared by radio-frequency (rf) magnetron sputtering. The effect oi oxygen concentration in the sputtering ambient on the structure and properties oi ITO films are investigated. The films have a preferred orientation in the (440) plane. The presence of oxygen during sputtering enhances the crystallization of the film. Film grain size increases as more oxygen is added. According to the XPS measurements, the addition of oxygen reduces the oxygen-deficient region of the film. Hence the optical transmittance of the film is improved while film conductivity decreases.
Detection of coherent signals using weighted subspace smoothing
(1996-02-01)
Ma, CW
;
Teng, CC
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
A new approach to detecting the number of coherent signals incident upon a uniformly-spaced linear array is presented. The approach combines a modified spatial smoothing scheme and a modified MDL criterion. The modified spatial smoothing scheme, referred to as ''weighted subspace smoothing,'' is actually a generalization of the ''post-smoothing'' approach proposed by Krim and Proakis in 1994. It is shown that the noise eigenvalues obtained with weighted subspace smoothing are more accurate than those obtained with the original spatial smoothing. We thus attempt to improve detection performance using these more accurate eigenvalues. A novel modification of the minimum description length (MDL) criterion is proposed to accomplish this. Computer simulations are presented to study the performance improvement of this new approach.
An efficient improvement for barrier effect of W-filled contact
(1996-02-01)
Yeh, WK
;
Chan, KY
;
Chang, TC
;
Tsai, MH
;
Chen, SH
A post chemical vapor deposition of tungsten (CVD-W) treatment by N-2 plasma is proposed to suppress the WAl12 formation during subsequent thermal annealing, which improves the thermal stability of W-filled contact. Selective CVD-W is employed to fill the contact hole. Following W deposition, in situ N-2 plasma treatment is performed prior to Al alloy metallization. It is shown that this post CVD-W treatment efficiently suppresses the formation of WAl12, resulting in an improvement of the barrier capability of W-filled contact.
The surface effect on Au 4f X-ray photoelectron spectra
(1996-02-01)
Wang, JP
;
Tung, CJ
;
Chen, YF
;
Kwei, CM
;
電子工程學系及電子研究所
An investigation of the surface effect on Au 4f X-ray photoelectron spectra was made for different emission angles, It was found that surface plasmon excitations made significant contributions to the spectra in single and plural energy-loss peaks and in the multiple loss background, Our approach involved Monte Carlo simulations of photoelectrons in the interior region of the solid and Poisson stochastic processes in the surface region. The partial-wave expansion method with the Hartree-Fock-Wigner-Seitz potential for the solid was used to calculate differential electron elastic scattering cross sections. An extended Drude dielectric function model was employed to compute electron differential inverse mean free paths for volume excitations. The inelastic mean free paths in the surface region became spatially-varying and were calculated. Differential probabilities for surface excitations were determined using the same model dielectric function. The computed X-ray photoelectron spectra including surface excitations agreed quite well with experimental data.
Quadrilevel periodic sequences for fast start-up equalization and channel estimation
(1996-02-01)
Liu, GS
;
Wei, CH
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電控工程研究所
;
Institute of Electrical and Control Engineering
A class of four-level periodic sequences derived from the binary m-sequences are presented. These sequences can be used as the training sequences in adaptive channel estimation and equalization with fast start-up for multilevel PAM or QAM transmission. The sequence generator can be implemented by simple hardware.
Relation-based variations of the discrete radon transform
(1996-02-01)
Hsueh, YC
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交大名義發表
;
資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
The finite Radon transform was introduced by Bolker around 1976. Since then, many variations of the discrete Radon transform have been proposed. In this paper, we first propose a variation of the discrete Radon transform which is based on a binary relation. Then, we generalize this variation to weighted Radon transformation based on a weighted relation. Under such generalization, we show that discrete convolution is a special case of weighted Radon transformation. To further generalize Radon transformation to be defined on lattice-valued functions, we propose two nonlinear variations of Radon transformation. These two nonlinear variations have very close relations with morphological operations. Finally, we generalize Matheron's representation theorem to represent translation-invariant operations on functions from an abelian group to a complete lattice.
Formation of cobalt silicided shallow junction using implant into through silicide technology and low temperature furnace annealing
(1996-02-01)
Chen, BS
;
Chen, MC
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work investigates the shallow CoSi2 contacted junctions formed by BF2+ and As+ implantation, respectively, into/through cobalt silicide followed by low temperature furnace annealing, For p(+)n junctions fabricated by 20 keV BF2+ implantation to a dose of 5 x 10(15) cm(-2), diodes with a leakage current density less than 2 nA/cm(2) at 5 V reverse bias can be achieved by a 700 degrees C/60 min annealing. This diode has a junction depth less than 0.08 mu m measured from the original silicon surface, For n(+)p junctions fabricated by 40 keV As+ implantation to a dose of 5 x 10(15) cm(-2), diodes with a leakage current density less than 5 nA/cm(2) at 5 V reverse bias can be achieved by a 700 degrees C/90 min annealing; the junction depth is about 0.1 mu m measured from the original silicon surface. Since the As+ implanted silicide film exhibited degraded characteristics, an additional fluorine implantation was conducted to improve the stability of the thin silicide film, The fluorine implantation can improve the silicide/silicon interface morphology, but it also introduces extra defects. Thus, one should determine a tradeoff between junction characteristics, silicide film resistivity, and annealing temperature.
Characterization of anodic aluminum oxide film and its application to amorphous silicon thin film transistors
(1996-02-01)
Liang, CW
;
Luo, TC
;
Feng, MS
;
Cheng, HC
;
Su, D
AL(2)O(3)/SINx double-layered dielectric films suitable for large-size amorphous silicon thin film transistor liquid crystal displays (a-Si:H TFT LCD) have been prepared by anodization and plasma enhanced chemical vapor deposition (PECVD). Al2O3 films were formed at various pH values and volume ratio of water (H2O%) in the electrolyte. The optimal quality of Al2O3 film was achieved at pH = 6 and H2O% = 30. These high-quality Al2O3 films have denser structure, lower etching rate (90 Angstrom min(-1)) and smooth surface morphology after etching. The capacitors made of the anodization show a breakdown field as high as 7.8 MV cm(-1) and a low leakage current density of 10 nA cm(-2) at a dielectric field of 3 MV cm(-1). Furthermore, a-Si:H TFTs with Al gate and different gate dielectrics (Al2O3/SINx and SiNx) were also fabricated and evaluated. The TFTs with Al2O3/SiNx double-layered gate dielectric provide better performances, such as the smaller threshold voltage (1.76 V), improved subthreshold swing (1.0 V dec(-1)), and lower off-current (3.8 PA) than those of the device with single SiNx, film.
Finite element modelling for land displacements due to pumping
(1996-02-01)
Yeh, HD
;
Lu, RH
;
Yeh, GT
;
土木工程學系
;
環境工程研究所
Equations of equilibrium (force balance) and flow in multidimensions were coupled in this paper to describe land displacements due to pressure decline in aquifers. A Galerkin finite element model based on these equations was developed. The saturated/unsaturated behaviour and the isotropic/anisotropic properties of permeability and elasticity were considered when the model was formulated. This model was verified by comparing its simulation results with those of known analytical solutions for simplified cases. The simulation of displacements due to pressure decline in unsaturated media was also performed. Those results demonstrated that the choice of boundary ranges for an aquifer with infinite domain may significantly affect the estimated horizontal and vertical displacements. To obtain a good estimation of land displacements, the boundary ranges should be carefully chosen. The displacements occurring in unconfined aquifers are caused by the drop of the water table and the change in body force in the dewatering zone. Simulation results also indicated that the change in body force should be considered once an unconfined aquifer has been pumped. Otherwise, the horizontal and vertical displacements in unconfined aquifers would be overestimated and underestimated, respectively. The behaviour of land displacements due to pumping was shown to be affected by changes in the total stresses in aquifers.