Browsing by Author "TSAI, WC"

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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.
BORON INCORPORATION IN SI1-XGEX FILMS GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION USING SI2H6 AND GEH4
(1995-11-13)
CHEN, LP
;
CHOU, CT
;
HUANG, GW
;
TSAI, WC
;
CHANG, CY
0.1% B2H6 diluted in hydrogen is used as the p-type dopant gas in Si1-xGex grown by ultrahigh vacuum chemical vapor deposition (UHVCVD) using Si2H6 and GeH4. The boron concentration is evaluated by secondary ion mass spectrometry (SIMS). The boron concentration of Si1-xGex increases with the increase of the GeH4 flow rate, that is, Ge fraction, by keeping Si2H6 and B2H6 how rates constant. The result may be due to the increase of the vacant surface sites which is caused by the increase of the hydrogen desorption rate when a higher Ge fraction epilayer is grown. (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.
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).
EPITAXY OF SI1-XGEX BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION USING SI2H6 AND GEH4
(1995-07-15)
CHEN, LP
;
CHOU, TC
;
TSAI, WC
;
HUANG, GW
;
TSENG, HC
Disilane and germane were used to grow Si1-xGex epilayers at 550 degrees C by ultrahigh-vacuum chemical vapor deposition (UHVCVD). The solid composition x and growth rate of Si1-xGex were evaluated from double-crystal X-ray rocking curves and show very strong dependence on the total source gas flow rate ([GeH4]+[Si2H6]) and the gas ratio ([GeH4]/[GeH4]+[Si2H6]). The solid composition increases with increase of the gas ratio and also with increasing the total source flux by keeping gas ratio constant. The growth rate increases with the solid composition at lower values and then becomes saturated in the higher composition range (x>0.22). The results can be explained by the relationships of the source fluxes, relative incorporation efficiency at activated surface sites and hydrogen desorption under different growth conditions.
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.
PRESSURE EFFECT ON YBA2CU3O7 THIN-FILM GROWTH IN OFF-AXIS RADIO-FREQUENCY MAGNETRON SPUTTERING
(1995-09-01)
WU, SC
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TSAI, WC
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HUANG, CK
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HSU, HT
;
HUANG, CJ
YBa2CU3O7-x (123) thin films were fabricated on (100) MgO substrates by off-axis single target radio frequency (rf) magnetron sputtering. Our study focused on the effect of chamber pressure on the composition, microstructure, and superconductive properties on transition behavior and T-c, of the grown him studied. An empirical formula was derived to explain the dependence of the deposition rate of various components on the pressure. Next, we compared the transport mechanism of the sputtered particles between the off-axis rf and the on-axis direct current sputtering and determined the processing conditions that result in superconducting films of better quality. According to our findings, growth at higher pressures (>100 mTorr) produces more homogeneous and higher T-c superconducting films. (C) 1995 American Vacuum Society.
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.