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NOVEL ALGAAS/GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS FABRICATED BY 2-STAGE MOLECULAR-BEAM EPITAXY
(1993-04-01)
CHEN, HR
;
CHANG, CY
;
TSAI, KL
;
TSANG, JS
;
LEE, CP
Two-stage molecular beam epitaxy (MBE) growth was employed to fabricate AlGaAs/GaAs heterojunction bipolar transistors (HBTs) for the first time. Due to the unique base contact layer design, the base can be made very thin without increasing the extrinsic base sheet resistance and the etching of the base contact can be done very easily and very reliably. In addition, the base-collector separation layer design contributed to the reduction of parasitic capacitance. D.C. differential current gains up to 110 and 200 were obtained for 1000 and 500 angstrom base width, respectively.
FUNDAMENTAL MODE-OPERATION OF HIGH-POWER INGAAS/GAAS/ALGAAS LASER ARRAYS
(1993-05-01)
TSANG, JS
;
LIOU, DC
;
TSAI, KL
;
CHEN, HR
;
TSAI, CM
A new ridge waveguide laser array with stable fundamental mode operation has been fabricated. By introducing absorption regions in all the laser stripes except for the central one, the electric field distribution of the laser arrays and the modal gains of the array supermodes are changed, resulting in fundamental mode operation. The threshold current of an array with five elements is typically 40 mA and the maximum output power is higher than 150 mW. The single-lobed far-field pattern centered at 0-degrees with full width at half maximum of 2-degrees is obtained at 1.5 times of the threshold current (I(th)).
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.
2-COLOR INFRARED PHOTODETECTOR USING GAAS/ALGAAS AND STRAINED INGAAS/ALGAAS MULTIQUANTUM WELLS
(1993-06-28)
TSAI, KL
;
CHANG, KH
;
LEE, CP
;
HUANG, KF
;
TSANG, JS
A two-color infrared detector using GaAs/A]GaAs and strained InGaAs/AlGaAs multiquantum wells is demonstrated. The response peak of the GaAs/AlGaAs quantum well is at 8 mum, and that of the InGaAs/AlGaAs quantum well is at 5.3 mum. The responsivity of the detector is 1 A/W at 8 mum and 0.27 A/W at 5.3 mum; these are the best values reported for a two-color quantum well infrared detectors (QWIPs) with peak sensitivities in the spectral regions of 3-5.3 mum and 7.5-14 mum. Single-colored 5.3 and 8 mum QWIPs were also fabricated to study the bias dependent behavior. This behavior can be explained using the concept of current continuity. Because of a higher electrical resistance, a high electric field domain is always formed first in the shorter wavelength quantum well stack.
THE STUDY OF EMITTER THICKNESS EFFECT ON THE HETEROSTRUCTURE EMITTER BIPOLAR-TRANSISTORS
(1993-07-15)
CHEN, HR
;
LEE, CP
;
CHANG, CY
;
TSANG, JS
;
TSAI, KL
AlGaAs/GaAs heterostructure emitter bipolar transistors were grown with emitter thicknesses varied from 300 to 900 angstrom and the emitter thickness effects on the current gain and offset voltage were studied. It was found that both the current gain and offset voltage are strongly dependent on the emitter thickness. The current gain decreases with increasing emitter thickness. For an emitter thickness smaller than 500 angstrom, the offset voltage decreases with increasing emitter thickness, but for an emitter thickness larger than 500 angstrom, the offset voltage stays at a nearly constant value. Offset voltage as low as 55 mV was obtained for an emitter thickness of 700 angstrom. This low offset voltage, mostly contributed by the geometric effect, indicates that the base-emitter junction is a homojunction. From the current gain and offset voltage considerations, the optimal emitter thickness was found to be about 300-500 angstrom.
EVIDENCE OF ZERO POTENTIAL SPIKE ENERGY IN ALGAAS GAAS HETEROSTRUCTURE EMITTER BIPOLAR-TRANSISTORS
(1993-10-01)
CHEN, HR
;
LEE, CP
;
CHANG, CY
;
TSAI, KL
;
TSANG, JS
The potential spike energy at the emitter junction of AlGaAs/GaAs heterostructure emitter bipolar transistors (HEBT) was directly measured for the first time. Experimental data revealed that emitter thickness as thin as 300 angstrom is thick enough to eliminate potential spike without compositional grading. It is found that the band bending in n-GaAs reduces the potential spike and hence very low offset voltage of 70 mV with high current gain of 150 can be obtained.
CURRENT GAINS OF ALAS/GAAS TUNNELING EMITTER BIPOLAR-TRANSISTORS WITH 25-500-ANGSTROM BARRIER THICKNESS
(1993-10-14)
CHEN, HR
;
LEE, CP
;
CHANG, CY
;
TSAI, KL
;
TSANG, JS
The current gain of an AlAs/GaS tunnelling emitter bipolar transistor (TEBT) is found to increase monotonically with barrier thickness in the range 25-200 angstrom and fall off for barrier thickness increasing from 200 to 500 angstrom. It is found that a thicker barrier can suppress the base-to-emitter hole injection better and increase the current gain, but a barrier which is too thick decreases the current gain due to the suppression of the electron current.
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.
DUAL-WAVELENGTH BRAGG REFLECTORS USING GAAS/ALAS MULTILAYERS
(1993-10-28)
LEE, CP
;
TSAI, CM
;
TSANG, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Dual-wavelength Bragg reflectors have been demonstrated using GaAs/AlAs multilayer heterostructures. Desired reflection bands can be obtained by adding proper phase shifters in a GaAs/AlAs periodic multilayer structure. The structure is based on the digital representation of the addition of two periodic functions.
COMPOSITION MODULATION OF INXGA1-XAS QUANTUM-WELLS BY FAST DIMER ARSENIC FLUX CHANGE USING VALVED ARSENIC CRACKER
(1994-01-01)
LIU, DC
;
LEE, CP
;
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.

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