Browsing by Author "Fan, JC"

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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.
Enhancement of Subnikov-de Haas oscillations by microwave radiation
(1997-12-01)
Fan, JC
;
Chang, YH
;
Chen, YF
;
Whang, JF
;
Fang, FF
We report for the first time that the Subnikov-de Haas (SdH) pattern can be greatly enhanced by recording the changes in the quantum oscillations of magnetoresistance due to microwave radiation. In order to understand the origin of the enhancement, the dependence of the enhanced SdH signal on temperature, microwave frequency and power has been studied. It is concluded that the enhancement can be attributed to the effects of free carrier absorption and the suppression of the nonoscillatory magnetoresistance. The technique shown here can be used to detect the SdH oscillations at relatively high temperature and in samples with moderate mobilities without perturbing the carrier concentration.
Low-resistance vertical conduction across epitaxially lifted-off n-GaAs film and Pd/Ge/Pd coated Si substrate
(1998-03-01)
Fan, JC
;
Tsai, CM
;
Chen, KY
;
Wang, SY
;
Lin, G
Low-resistance ohmic conduction across an epitaxially lifted-off(ELO) thin n-GaAs film and a Si substrate was obtained by attaching the ELO film on the Si substrate coated with a Pd/Ge/Pd multilayer. Good bonding and ohmic contacts to both GaAs and Si were achieved at the same time after annealing. The interface compound formation was studied by secondary ion mass spectroscopy and x-ray diffraction analyses. This ELO technology was used to fabricate an ELO stripe geometry diode laser on Si with the back-side contact on Si substrate. Good laser performance with comparable characteristics as conventional laser diodes on GaAs substrates was obtained.
Optical and structural properties of epitaxially lifted-off GaAs films
(1998-01-01)
Fan, JC
;
Lee, CP
;
Tsai, CM
;
Wang, SY
;
Tsang, JS
The influence of the layer thickness on the optical and structural properties of the epitaxially lifted-off (ELO) thin films has been studied. The ELO films bonded to Si, InP, and GaAs substrates have also been compared. The structure was characterized by high-resolution double-crystal x-ray diffraction and the optical properties were measured by the temperature-dependent photoluminescence spectroscopy. A biaxial compressive strain was observed for the samples bonded to Si with a buffer layer thinner than 1000 nm. Due to different thermal expansion coefficient between the grafted thin film and the host substrate, the emission spectra of the quantum wells of the lifted-off thin films are redshifted compared to the as-grown sample. The amount of the redshift is larger for thinner films. (C) 1998 American Institute of Physics.
Persistent photoconductivity in SiGe/Si quantum wells
(1998-07-15)
Tsai, LC
;
Huang, CF
;
Fan, JC
;
Chang, YH
;
Chen, YF
Persistent photoconductivity (PPC) has been observed in boron-doped Si1-xGex/Si quantum wells. The decay kinetics of the PPC effect can be well described by a stretched-exponential function, I-ppc(t) = I-ppc(0)exp[-(t/tau)(beta)](0 < beta < 1), which is usually observed in many disorder materials. Through the studies of the PPC effect under various conditions, such as different temperature, different photon energy of photoexcitation, and different Ge content, we identify that the alloy potential fluctuations induced by compositional disorder are the origin of the PPC effect in Si1-xGex/Si quantum wells. (C) 1998 American Institute of Physics. [S0021-8979(98)00914-1].
Stripe-geometry GaAs-InGaAs laser diode with back-side contact on silicon by epitaxial lift-off
(1997-06-05)
Fan, JC
;
Chen, KY
;
Lin, G
;
Lee, CP
;
電子工程學系及電子研究所
The transfer of a preprocessed stripe-geometry GaAs-InGaAs laser diode film onto a Pd/Ge/Pd coated n(+)-Si substrate is reported with the backside contact on Si using epitaxial lifted-off (ELO) technology. The Pd/Ge/Pd metal layers provide ohmic contacts to both the Si substrate and the GaAs film, making vertical conduction through the Si substrate possible. No device degradation was observed after the ELO process and comparable results were obtained for the ELO laser diodes and the diodes without the ELO process.
Stripe-geometry GaAs-InGaAs laser diode with back-side contact on silicon by epitaxial lift-off
(1997-06-05)
Fan, JC
;
Chen, KY
;
Lin, G
;
Lee, CP
;
電子工程學系及電子研究所
The transfer of a preprocessed stripe-geometry GaAs-InGaAs laser diode film onto a Pd/Ge/Pd coated n(+)-Si substrate is reported with the backside contact on Si using epitaxial lifted-off (ELO) technology. The Pd/Ge/Pd metal layers provide ohmic contacts to both the Si substrate and the GaAs film, making vertical conduction through the Si substrate possible. No device degradation was observed after the ELO process and comparable results were obtained for the ELO laser diodes and the diodes without the ELO process.
The effect of barrier structure on the performance of double barrier quantum well infra-red photodetectors
(1996-02-01)
Tsai, KL
;
Lee, CP
;
Chen, PC
;
Tsang, JS
;
Tsai, CM
The effects of the inner and outer barriers on the performance of mid-wavelength (3-5 mu m) GaAs/AlGaAs double barrier quantum well infra-red photodetectors (DBQWIPs) have been studied. It was found that the peak response wavelength had a significant red shift when the thickness of the AlAs inner barriers was below 10 Angstrom. This is attributed to the lowering of the upper state energy in the quantum wells. The responsivity of DBQWIPs decreases with the inner barrier thickness. This is because the optical gain decreases faster than the increasing rate of the quantum efficiency when the inner barrier thickness increases. The responsivities for devices with different Al compositions (0.35 and 0.24) in the outer barriers are in the same range, but the dark currents for devices with Al(0.35)G(0.65)As outer barriers are much lower than those with Al0.24Ga0.76As outer barriers. Nearly two orders of magnitude improvement in detectivity was observed when the Al composition in the outer barriers was changed from 0.24 to 0.35. A high detectivity of 1 x 10(11) cm Hz(1/2) W-1 at 77 K was obtained for a device with 12 Angstrom AlAs inner barriers and 300 Angstrom Al0.35Ga0.65As outer barriers.
Thermal annealing of Pd/InAlAs Schottky contacts for transistor buried-gate technologies
(1998-01-01)
Chuang, HF
;
Lee, CP
;
Tsai, CM
;
Liu, DC
;
Tsang, JS
We studied the thermal reaction of Pd/In0.52Al0.48As contacts using capacitance-voltage (C-V), current-voltage, Auger electron spectroscopy, and x-ray diffraction analyses and compared the results to those for Pd/Al0.25Ga0.75As and Pd/In0.53Ga0.47As contacts. The thickness of InAlAs consumed by the reaction during annealing was calculated directly from the measured C-V profiles. Pd starts to react with InAlAs at a temperature of 100 degrees C, lower than it does with AlGaAs. For thermally annealed Pd/InAlAs and Pd/AlGaAs, both compositional and structural changes were found at the Pd/semiconductor interface. However, in heat-treated Pd/InGaAs samples, compositional changes but no structural changes were observed. (C) 1998 American Institute of Physics.
Thermal annealing of Pd/InAlAs Schottky contacts for transistor buried-gate technologies
(1998-01-01)
Chuang, HF
;
Lee, CP
;
Tsai, CM
;
Liu, DC
;
Tsang, JS
We studied the thermal reaction of Pd/In0.52Al0.48As contacts using capacitance-voltage (C-V), current-voltage, Auger electron spectroscopy, and x-ray diffraction analyses and compared the results to those for Pd/Al0.25Ga0.75As and Pd/In0.53Ga0.47As contacts. The thickness of InAlAs consumed by the reaction during annealing was calculated directly from the measured C-V profiles. Pd starts to react with InAlAs at a temperature of 100 degrees C, lower than it does with AlGaAs. For thermally annealed Pd/InAlAs and Pd/AlGaAs, both compositional and structural changes were found at the Pd/semiconductor interface. However, in heat-treated Pd/InGaAs samples, compositional changes but no structural changes were observed. (C) 1998 American Institute of Physics.
Thermal reactions of Pd/AlxGa1-xAs contacts
(1996-09-01)
Chuang, HF
;
Lee, CP
;
Tsang, JS
;
Fan, JC
;
電子工程學系及電子研究所
Pd/AlxGa1-xAs Schottky contacts and their thermal reactions are studied by capacitance-voltage measurements, current-voltage measurements, and x-ray diffraction. The thickness of AlxGa1-xAs consumed by the Pd/AlxGa1-xAs reaction during annealing was calculated. For annealing temperatures below 300 degrees C the Schottky characteristics of the diodes were good but the electrical junction moves into AlxGa1-xAs after annealing. The amount of junction movement was calculated directly from our measurements. The diffusion coefficients of Pd in AlxGa1-xAs and the activation energy were estimated. The activation energy was found to be larger for higher Al concentration. PdAl, PdAs2, PdGa5, and Pd5Ga2 were detected in the compounds formed by the Pd/AlxGa1-xAs reaction after annealing. (C) 1996 American Institute of Physics.
Thermal reactions of Pd/AlxGa1-xAs contacts
(1996-09-01)
Chuang, HF
;
Lee, CP
;
Tsang, JS
;
Fan, JC
;
電子工程學系及電子研究所
Pd/AlxGa1-xAs Schottky contacts and their thermal reactions are studied by capacitance-voltage measurements, current-voltage measurements, and x-ray diffraction. The thickness of AlxGa1-xAs consumed by the Pd/AlxGa1-xAs reaction during annealing was calculated. For annealing temperatures below 300 degrees C the Schottky characteristics of the diodes were good but the electrical junction moves into AlxGa1-xAs after annealing. The amount of junction movement was calculated directly from our measurements. The diffusion coefficients of Pd in AlxGa1-xAs and the activation energy were estimated. The activation energy was found to be larger for higher Al concentration. PdAl, PdAs2, PdGa5, and Pd5Ga2 were detected in the compounds formed by the Pd/AlxGa1-xAs reaction after annealing. (C) 1996 American Institute of Physics.