Browsing by Author "LIU, DC"

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AN ELECTRICAL METHOD TO CHARACTERIZE THERMAL-REACTIONS OF PD/GAAS AND NI/GAAS CONTACTS
(1995-06-01)
CHUANG, HF
;
LEE, CP
;
LIU, DC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Capacitance-voltage (C-V) and current-voltage (I-V) measurements were used to study the thermal reaction of Pd/GaAs contacts and Ni/GaAs contacts. The thickness of GaAs consumed by the metal/GaAs reaction during annealing was calculated from C-V analyses and I-V analyses. For annealing temperatures below 350 degrees C, the Schottky characteristics of the diodes were good but the electrical junction moves into the GaAs after annealing. The amount of junction movement was calculated directly from our measurements. The diffusion coefficients of Pd and Ni in GaAs at 300 degrees C were estimated both to be around 1.2 x 10(-14) cm(2)/s.
ASYMMETRIC DARK CURRENT IN QUANTUM-WELL INFRARED PHOTODETECTORS
(1994-05-02)
TSAI, KL
;
LEE, CP
;
CHANG, KH
;
LIU, DC
;
CHEN, HR
Asymmetric dark current versus voltage characteristics in quantum weil infrared photodetectors have been studied. A model based on asymmetrical potential barriers was proposed. The asymmetrical potential barriers, which are most likely due to the accumulation of oxygen impurities at one of the interfaces, cause the asymmetrical I-V characteristics. The height of the potential spike is found to increase with the Al content in the AlGaAs barriers. Calculations based on our model agree well with experimental results.
COMPOSITION MODULATION OF INXGA1-XAS QUANTUM-WELLS BY FAST DIMER ARSENIC FLUX CHANGE USING VALVED ARSENIC CRACKER
(1994-01-01)
LIU, DC
;
LEE, CP
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TSAI, KL
;
TSANG, JS
;
CHEN, HR
By fast change of the As-2 flux using a high temperature valved cracker, we have demonstrated the growth of strained InxGa1-xAs quantum wells with different compositions. The modulation of composition is due to the change in incorporation rates of the group III atoms under different As-2 fluxes. Photoluminescence (PL) emission from the quantum wells clearly indicates the change in composition. A change of In composition from 20.6% to 8.5%, has been achieved by changing the V/III beam-equivalent-pressure (BEP) ratio from 11.7 to 3.9. By this technique of composition modulation, we have fabricated strained InxGa1-xAs/GaAs single quantum well lasers with different emission wavelengths.
ENHANCEMENT OF ELECTRON-WAVE REFLECTION BY SUPERLATTICES WITH MULTIPLE STACKS OF MULTIQUANTUM BARRIERS
(1994-02-28)
YEN, ST
;
TSAI, CM
;
LEE, CP
;
LIU, DC
;
電子工程學系及電子研究所
We report a superlattice (SL) with multiple stacks of multiquantum barriers (MQB), which can reflect electrons more effectively than with a single stack of MQB. The reflectivities are calculated and compared with one another for a variety of potential barrier structures. The multistack SL has a wider energy spectrum within which electrons are reflected. Four types of n-GaAs/i-barrier/n-GaAs diodes were fabricated to confirm the calculated results. The current-voltage characteristics measured at 77 K for these diodes show that the turn-on voltage increases with the number of stacks of MQBs in the SL. This is in agreement with our calculated results.
ENHANCEMENT OF ELECTRON-WAVE REFLECTION BY SUPERLATTICES WITH MULTIPLE STACKS OF MULTIQUANTUM BARRIERS
(1994-02-28)
YEN, ST
;
TSAI, CM
;
LEE, CP
;
LIU, DC
;
電子工程學系及電子研究所
We report a superlattice (SL) with multiple stacks of multiquantum barriers (MQB), which can reflect electrons more effectively than with a single stack of MQB. The reflectivities are calculated and compared with one another for a variety of potential barrier structures. The multistack SL has a wider energy spectrum within which electrons are reflected. Four types of n-GaAs/i-barrier/n-GaAs diodes were fabricated to confirm the calculated results. The current-voltage characteristics measured at 77 K for these diodes show that the turn-on voltage increases with the number of stacks of MQBs in the SL. This is in agreement with our calculated results.
INVESTIGATION OF INDIUM DOPING IN INGAAS GAAS ALGAAS GRADED-INDEX SEPARATED CONFINEMENT HETEROSTRUCTURE LASERS
(1993-10-15)
TSANG, JS
;
LEE, CP
;
LIU, DC
;
CHEN, HR
;
TSAI, KL
The effect of indium doping in the graded-index regions of the InGaAs/GaAs/AlGaAs graded-index separated confinement heterostructure quantum well laser has been studied. It was found that the threshold current density can be greatly reduced by a proper amount of In doping in the graded AlGaAs region. This result is attributed to an improvement in material quality due to a reduction in group III vacancies. The effect of thermal treatment on laser performance has also been studied. Although high temperature annealing can significantly improve non-In-doped lasers, it has little effect on In-doped lasers.
NOVEL FABRICATION TECHNIQUE TOWARDS QUANTUM DOTS
(1993-12-20)
LIU, DC
;
LEE, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel technique for semiconductor quantum dots fabrication is demonstrated. Using the technique of thermal etching or thermal evaporation during molecular beam epitaxial growth with a built-in evaporation mask, semiconductor quantum dots were obtained in a single growth run.
ROLE OF CLADDING LAYER THICKNESSES ON STRAINED-LAYER INGAAS/GAAS SINGLE AND MULTIPLE-QUANTUM-WELL LASERS
(1993-06-15)
LIU, DC
;
LEE, CP
;
TSAI, CM
;
LEI, TF
;
TSANG, JS
The influences of cladding layer thicknesses on the performance of strained-layer InGaAs/GaAs graded-index separated confinement heterostructure quantum well lasers have been studied. The waveguiding property of the laser structure was analyzed using the transfer matrix method. In this work, experimental results and the calculated results showed that threshold current densities and external quantum efficiencies both were crucially dependent on the thicknesses of cladding layer for both single and multiple quantum well lasers. The minimum cladding layer thicknesses needed to maintain low threshold current densities and low internal total loss for both single and multiple quantum well devices were determined experimentally and theoretically.