Browsing by Author "CHANG, TC"

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A PRECISION ALIGNMENT WITH MOIRE TECHNIQUE AND DIFFERENTIAL-AMPLIFIER
(1992-06-01)
CHANG, TC
;
WU, CW
;
CHOU, C
;
光電工程學系
;
Department of Photonics
A precision alignment technique is developed. We combined a moire and a differential amplifier to align two Ronchi rulings with high accuracy. The precision of this technique can reach submicron level if higher spatial frequency of the ruling is used.
ABRUPTNESS OF GE COMPOSITION AT THE SI/SIGE INTERFACE GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1995-08-21)
TSAI, WC
;
CHANG, CY
;
JUNG, TG
;
LIOU, TS
;
HUANG, GW
A model is proposed to estimate the interfacial abruptness of the Si/SiGe heterojunction. In this model, a transition region with linearly graded Ge composition is assumed at the Si/SiGe interface. The Ge composition x of Si/SiGe quantum well grown by ultrahigh vacuum chemical vapor deposition at 550 degrees C is found to increase with the deposition time as deposition at the same gas phase composition. This phenomenon can be explained by this model and the fitting results match the measured data. The thickness of the transition region and the transition time can be extracted from these fittings. The transition thicknesses are found to be about 1.9 nm or thinner as grown at 550 degrees C or below. (C) 1995 American Institute of Physics.
CHARACTERIZATION OF SI/SIGE STRAINED-LAYER SUPERLATTICES GROWN BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION TECHNIQUE
(1994-04-01)
CHANG, TC
;
CHANG, CY
;
JUNG, TG
;
TSAI, WC
;
HUANG, GW
High-resolution double-crystal X-ray diffraction and cross-sectional transmission electron microscopy were used to characterize the Si/SiGe strained-layer superlattices grown by the ultrahigh vacuum/chemical vapor deposition (UHV/CVD) system. A dynamical X-ray simulation was employed to analyze the experimental rocking curves. Good matches between the experimental rocking curves and the simulated ones demonstrate that the high quality Si/SiGe strained-layer superlattices with abrupt interface and excellent thickness and composition uniformity have been achieved. Thickness uniformity was further confirmed by the cross-sectional transmission electron microscopy. In addition, high-resolution double-crystal X-ray diffraction was proven to be a powerful technique for determining the doping level and the thickness of heavily doped contact layer in Si/SiGe device structures prior to further processing. Good wafer-to-wafer uniformity can be simultaneously achieved by the UHV/CVD technique; as a result, the UHV/CVD technique is readily applicable to manufacturing.
CHARACTERIZATION OF THE SI/SIGE HETEROJUNCTION DIODE GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1994-10-15)
JUNG, TG
;
CHANG, CY
;
LIU, CS
;
CHANG, TC
;
LIN, HC
The unipolar Si/SiGe heterojunction diode grown by ultrahigh vacuum chemical vapor deposition at 550-degrees-C is demonstrated. The dark current density measured at 77 K is (2.5 +/- 0.1) x 10(-7) A/cm2 for the barrier height of 176 +/- 8 meV, at a reverse bias of 1 V. The barrier heights are measured from the activation analysis of the saturation current and compared to the theoretical values. The barrier height decreases as the thickness of the SiGe strained layer exceeds the critical thickness.
EFFECT OF CROSS-PHASE MODULATION ON OPTICAL-PHASE CONJUGATION IN DISPERSION-SHIFTED FIBER
(1994-07-01)
WEN, SF
;
CHI, S
;
CHANG, TC
;
光電工程學系
;
Department of Photonics
The temporal effect of optical phase conjugation in dispersion-shifted fiber is studied numerically. Frequency chirping is induced in the conjugate pulse by the signal pulse and the pump wave through cross-phase modulation, which increases with the signal power and may distort the pulse shape when the conjugate pulse propagates in the standard fiber. It is also shown that, when the signal power is low, the optical phase conjugation is nearly ideal.
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).
HIGH-RESOLUTION X-RAY CHARACTERIZATION OF LOW-TEMPERATURE GAAS/AS SUPERLATTICE GROWN BY MOLECULAR-BEAM EPITAXY
(1994-06-27)
CHENG, TM
;
CHANG, CY
;
CHANG, TC
;
HUANG, JH
;
HUANG, MF
High-resolution x-ray analysis of Si delta-doped GaAs grown by molecular-beam epitaxy at a low substrate temperature (230-degrees-C) is presented. Superlattice satellite peaks in the rocking curve are observed for the sample annealed at 700-degrees-C for 10 min. The peak intensity increases with increasing postgrowth annealing temperature and reaches the maximum value for the 900-degrees-C annealed sample. The evolution of the x-ray rocking curves can be explained consistently by the formation of a GaAs/As superlattice during the annealing period based on the transmission electron microscope observations.
INFORMATION RATE OF MCELIECE PUBLIC-KEY CRYPTOSYSTEM
(1990-01-04)
LIN, MC
;
CHANG, TC
;
FU, HL
;
應用數學系
;
Department of Applied Mathematics
LOW-TEMPERATURE EPITAXIAL-GROWTH OF SILICON AND SILICON-GERMANIUM ALLOY BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1994-01-01)
JUNG, TG
;
CHANG, CY
;
CHANG, TC
;
LIN, HC
;
WANG, T
Low-temperature epitaxy of silicon and silicon-germanium alloy via an ultrahigh-vacuum chemical vapor deposition system was investigated. Bistable conditions were observed for silicon epitaxial growth performed within the temperature range of 550 degrees C to 800 degrees C. The activation energy of the SiGe growth rate was found to decrease as the germanium composition increased. The germanium atomic molar fraction in these epitaxial layers was tightly controlled by a computer-controlled gas source switching system. Si/SiGe superlattice structures of 20-period 5 nm Si/12 nm SiGe layers were grown to demonstrate the excellent controllability of this growth technique.
NANOMETER THICK SI/SIGE STRAINED-LAYER SUPERLATTICES GROWN BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION TECHNIQUE
(1994-04-01)
CHANG, TC
;
CHANG, CY
;
JUNG, TG
;
TSAI, WC
;
WANG, PJ
High quality Si/Si1-xGex superlattices having layers as thin as 1.5 nm have been grown by an ultrahigh vacuum/chemical vapor deposition system. High-resolution double-crystal x-ray diffraction, and conventional and high-resolution cross-sectional transmission electron microscopy were used to evaluate the crystalline quality of these superlattices. A dynamical x-ray simulation program was employed to analyze the experimental rocking curves. Excellent matches between experimental rocking curves and simulated ones were obtained for all superlattices with various periodicity. A cross-sectional transmission electron micrograph of an 80 period Si(4.2 nm)/Si0.878Ge0.122 (1.5 nm) superlattice, in which each individual layers was clearly resolved, demonstrated the capability of this growth technique for nanometer thick layer deposition.
QUANTUM CONFINEMENT EFFECTS OF SI/SIGE STRAINED-LAYER SUPERLATTICES GROWN BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION TECHNIQUE
(1994-12-01)
CHANG, TC
;
CHANG, CY
;
JUNG, TG
;
CHEN, PA
;
TSAI, WC
Well-resolved band-edge luminescence is observed for Si0.86Ge0.14/Si strained-layer superlattices grown by an ultrahigh vacuum/chemical vapour deposition technique at 550 degrees C. High-resolution double-crystal X-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (XTEM) were used to determine the strain and other parameters for these strained-layer superlattices. Quantum confinement is observed for a SiGe well as thin as 1.3 nm. The blue shift of the emission peaks with decreasing well width is found to be in good agreement with theoretical calculation.
THE NOVEL NONLINEAR DC RESPONSE OF AG THIN-FILMS DEPOSITED ON POROUS SILICON - A FRACTAL MODEL EXPLANATION
(1995-11-15)
YOUNG, TF
;
KUO, WC
;
JIANG, IM
;
CHANG, TC
;
CHANG, CY
We have observed a novel non-linear de resistivity of Ag thin films deposited on porous silicon (PS) surfaces. We also found that as the porous silicon is oxidized in a HNO3 solution, the de resistivities of the Ag thin films become two orders of magnitude smaller, and behave linearly but are divided into three different regions. Each region exhibits different resistivities which drops abruptly at the thresholds. The resistivity decreases as the current increasing into a higher current region. The atomic force microscopy (AFM) image shows a self-affine structure of the PS surface with wires, hillocks and voids on various scales. After oxidation, the rough surface is smoothed down to simpler fractal hillock clusters. The silver clusters are deposited on the glazed surface in a fractal-like size distribution. A branched Koch curve fractal model is proposed in this study to model the tunneling between fractal-like silver clusters. It explains the stepwise linear fractal-like resistivity behavior.