Browsing by Author "Hsieh, KC"

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Direct evidence of Au segregation in laser welded Au-coated Invar material
(1997-08-01)
Wang, SC
;
Chi, S
;
Hsieh, KC
;
Yang, YD
;
Cheng, WH
Evidence of the Au segregation within the crack region in laser welded Au-coated Invar material for semiconductor laser packaging is investigated. Results obtained from the metallography, scanning electron microscope (SEM) mapping, energy dispersive spectrometer (EDS) Line profile,and Auger electron spectroscopy find that the cracks in the welded joints occur around the Au rich boundaries. The SEM Au mapping and EDS line profiles show that Au accumulates at the crack region. This direct observation indicates that one of the primary causes of cracks in laser welded Au-coated materials is due to the segregation of Au in the final stage of solidification. Detailed knowledge of the defect formation mechanisms in laser welded Au-coated materials is important for the practical design and fabrication of reliable optoelectronic packaging.
High quality ultrathin CoTiO3 high-k gate dielectrics
(2000-09-01)
Pan, TM
;
Lei, TF
;
Chao, TS
;
Chang, KL
;
Hsieh, KC
A novel high-k cobalt-titanium oxide (CoTiO3) was formed by directly oxidizing sputtered Co/Ti film. Al/CoTiO3/Si3N4/Si capacitor structure was fabricated and measured. The effective dielectric constant with buffered layer for CoTiO3 gate dielectric can reach as high as 40 while depicting excellent electrical properties at the same time. This novel metal oxide thus appears to be a promising high-k gate dielectric for future ultralarge scale integrated devices. (C) 2000 The Electrochemical Society. S1099-0062(00)03-095-9. All rights reserved.
Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures
(1996-07-15)
Chin, A
;
Chen, WJ
;
Ganikhanov, F
;
Lin, GR
;
Shieh, JM
Cross-sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70 degrees C, A columnar polycrystalline GaAs is observed for samples grown at 160 degrees C while it appears amorphous for samples grown at temperatures below 120 degrees C, The successful growth of amorphous (Ga,As) at 70 degrees C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As-4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as-grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (similar to 500 Angstrom in size) whose grain boundaries provide effective carrier traps and recombination centers. (C) 1996 American Institute of Physics.
Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures
(1996-07-15)
Chin, A
;
Chen, WJ
;
Ganikhanov, F
;
Lin, GR
;
Shieh, JM
Cross-sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70 degrees C, A columnar polycrystalline GaAs is observed for samples grown at 160 degrees C while it appears amorphous for samples grown at temperatures below 120 degrees C, The successful growth of amorphous (Ga,As) at 70 degrees C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As-4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as-grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (similar to 500 Angstrom in size) whose grain boundaries provide effective carrier traps and recombination centers. (C) 1996 American Institute of Physics.