Browsing by Author "JUANG, C"

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ANALYSIS OF DIFFERENTIAL GAIN IN GAAS/ALGAAS QUANTUM-WELL LASERS
(1994-07-01)
CHEN, PA
;
CHANG, CY
;
JUANG, C
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電控工程研究所
;
Institute of Electrical and Control Engineering
The differential gain of a quantum-well laser is studied theoretically with use of both a parabolic band model and a valence-band-mixing model. In the valence-band-mixing model, the gain profile is derived from the multiband effective mass theory (k.p method) as well as the density matrix formalism. The peak gain including the band-mixing effect is significantly reduced to 1.5-2 times when compared to the conventional parabolic band model. There is still a larger differential gain using the parabolic band model than using the band-mixing model. The magnitudes of differential gains for these two models give the order of 10(-16)-10(-15) cm2, which is in agreement with the experimental results. Besides, the quantum-well thickness also influences the differential gain, which is enhanced by a thinner quantum-well structure.
CARRIER-INDUCED ENERGY SHIFT IN GAAS/ALGAAS MULTIPLE-QUANTUM-WELL LASER-DIODES
(1993-10-01)
CHEN, PA
;
JUANG, C
;
CHANG, CY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Emission energy shift due to high carrier density at threshold in multiple quantum well (MQW) laser diodes is investigated theoretically. This energy shift is evaluated through the Schrodinger and the Poisson equations self-consistently as well as the calculation of the gain spectra with carrier-dependent lifetime broadening. The band filling and the gain broadening effects show a blue shift on the emission energy. Larger number of wells, lower barrier height, or wider well thickness, reduces the blue shift dependence on the carrier density. At high injections, this blue shift is offset by the bandgap shrinkage effect, which displays smaller influence on MQW's. While the carrier density is further increased, the transition due to the second quantized state is found in single quantum wells, however it is difficult to be observed in MQW's.
COMPRESSIVE AND TENSILE STRAIN EFFECTS ON HOLE TUNNELING IN AN INGAAS/ALLNAS ASYMMETRICAL COUPLED-QUANTUM-WELL
(1993-12-15)
CHEN, PA
;
CHANG, CY
;
JUANG, C
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Hole tunneling dynamics are investigated in a strained asymmetrical coupled quantum well (ACQW). The tunneling probabilities between heavy-hole states are calculated at different internal strains on the basis of the time-dependent Schrodinger equation analysis with the Luttinger-Kohn and an additional strain Hamiltonians. In a certain range of strain, a higher oscillation frequency (but a smaller oscillation amplitude) of hole tunneling at resonance is obtained in a biaxial tensile strain ACQW at in-plane wave vector k(parallel-to) = 0. The biaxial compressive strain is observed to lower the oscillation frequency. With a nonzero wave vector (k(parallel-to) not-equal 0), the oscillation frequency is found to be dominated by mixing effects and less dependent on the internal strain. The oscillation frequency remains roughly constant; however, the biaxial compressive strain ACQWs would still have a larger oscillation amplitude than biaxial tensile strain ACQWs.
ENERGY-STATES OF FINITE-BARRIER QUANTUM WIRES IN THE PRESENCE OF AN EXTERNAL ELECTRIC-FIELD
(1991-04-08)
JUANG, C
;
CHANG, CY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Energy level shift in finite-barrier quantum wires systems is found to be enhanced in comparison to finite-barrier single quantum well systems. The ground-state solutions of the two-dimensional Schrodinger equation are obtained using the inverse power method combined with the successive over relaxation method. In addition, the two-dimensional changes in the wave function due to an external electric field in cylindrical quantum wires are presented.
ORIENTATION DEPENDENCE OF COHERENT HOLE OSCILLATIONS IN GAAS/ALGAAS COUPLED QUANTUM-WELLS
(1995-07-01)
CHANG, CY
;
LU, MF
;
CHEN, PA
;
JUANG, C
;
電控工程研究所
Coherent hole tunneling dynamics in GaAs/AlGaAs coupled quantum wells (CQWs) based on (100)- and (111)-oriented GaAs substrates are investigated. The tunneling probability of the hole wave packet for a heavy-hole to heavy-hole (HH-HH) band and a light-hole to Light-hole (LH-LH) band is described based on the results of a time-dependent analysis. It is demonstrated that the CQW HH-HH oscillation frequency on (100) substrates is larger than that on (111) substrates due to a significantly lighter in-plane effective mass. However, the LH-LH spatial tunneling oscillation frequency on (100) substrates is smaller than that on (111) substrates.
VALENCE-BAND MIXING EFFECTS ON HOLE OSCILLATIONS IN COUPLED QUANTUM-WELLS
(1993-02-15)
JUANG, C
;
CHEN, PA
;
CHANG, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Valence-band mixing effects on the dynamics of the heavy- and light-hole oscillations in coupled quantum wells are described by a numerical implementation using the time-dependent Schrodinger equation with the Luttinger Hamiltonian. With a nonzero in-plane wave vector (k(parallel-to) not-equal 0), mixing tunneling (between heavy- and light-hole states) and spatial tunneling (from one well to the other) occur at the same time. This time-dependent analysis clearly resolves these two tunneling mechanisms and shows several effects which have not been addressed by previous time-independent analysis.