Browsing by Author "CHEN, PA"

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ANALYSIS OF DIFFERENTIAL GAIN IN GAAS/ALGAAS QUANTUM-WELL LASERS
(1994-07-01)
CHEN, PA
;
CHANG, CY
;
JUANG, C
;
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.
ANOMALOUS MOBILITY ENHANCEMENT IN HEAVILY CARBON-DOPED GAAS
(1994-05-15)
CHEN, HD
;
FENG, MS
;
LIN, KC
;
CHEN, PA
;
WU, CC
An anomalous mobility enhancement and metallic-type conductivity were observed in heavily carbon-doped GaAs grown by low-pressure metalorganic chemical vapor deposition. The 77 K mobility was slightly lower than that of 300 K for hole concentration between 1 x 10(18) and 4 x 10(18) cm-3. However, the 77 K mobility was enhanced from p > 4 X 10(18) cm-3, and the 300 K mobility slowly decreased with increasing hole concentration that ranged from 7 X 10(18) to 3 X 10(19) cm -3. As a result, the 77 K mobility was around 50%-60% greater than the 300 K mobility due to the metallic-type conductivity.
BACK-GATING EFFECTS ON THE GA0.1IN0.8P/INP/INGAAS HIGH-ELECTRON-MOBILITY TRANSISTOR
(1995-07-01)
LIN, KC
;
CHANG, CY
;
WU, CC
;
CHEN, HD
;
CHEN, PA
Pseudomorphic GaInP/InP/InGaAs high electron mobility transistors (HEMT) with improved Schottky contacts and excellent electrical characteristics are grown by low-pressure metal-organic chemical vapor deposition (LP-MOCVD) on the InP substrate. These HEMTs with 1.71 mu m gate length have an average extrinsic transconductance of 225 mS/mm. The back-gating effects of this device structure are investigated for the first time in this structure. Both positive and negative bias are applied to the ohmic and Schottky back-gate contacts of these devices. The positive back-gate bias has no effect on the drain current or the output transconductances of these devices. The effect of the negative back-gate bias is very similar to that when negative bias is applied on the gate of these HEMTs.
CARBON INCORPORATION DURING GROWTH OF GAAS BY TEGA-ASH3 BASE LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1993-06-01)
CHEN, HD
;
CHANG, CY
;
LIN, KC
;
CHAN, SH
;
FENG, MS
Heavily carbon-doped GaAs (1 X 10(18) approximately 1 X 10(20) cm-3) grown by low-pressure metalorganic chemical vapor deposition using triethylgallium and arsine as sources and liquid carbon-tetrachloride (CCl4) as dopant has been investigated. The carrier concentration was verified at various growth temperatures, V/III ratios, and CC]4 flow rates. Dopant concentration first increased from 550-degrees-C and reached a maximum at 570-degrees-C growth temperature (T(g)) and then decreased monotonously. Carbon incorporation was strongly enhanced when the V/III ratio was less than 30 at T(g) = 590-degrees-C or less than 40 at T(g) = 630-degrees-C. Hole concentration increased and then decreased as CCl4 flow rate increased. Growth rate of layers decreased as growth temperature and flow rate Of CCl4 increased. The doping efficiency of epitaxial layers grown on the (100) substrate was higher than that on the 2-degrees off toward [110] misoriented substrate. Carbon-doped GaAs films had higher Hall mobility than zinc-doped GaAs films at high doping levels due to less self-compensation. The highest dopant concentration in this system was 2.3 X 10(20) cm-3 at T(g) = 580-degrees-C and V/III = 10.
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.
CATION SOURCE DEPENDENCE OF GA0.5IN0.5P GROWTH-RATE BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-06-15)
WU, JW
;
CHANG, CY
;
LIN, KC
;
CHAN, SH
;
CHEN, HD
The Ga0.5In0.5P epilayer was grown by low-pressure metalorganic chemical vapor deposition. Trimethylgallium and triethylgallium were used as the gallium source's, while trimethylindium and ethyldimethylindium were used as the indium sources. The use of triethylgallium incorporated with trimethylindium enhanced the growth rate of Ga0.5In0.5P as compared to incorporation with ethyldimethylindium. While the use of trimethylgallium incorporated with ethyldimethylindium enhanced the growth rate of Ga0.5In0.5P significantly, as compared to incorporation with trimethylindium.
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.
LOW-TEMPERATURE LUMINESCENT PROPERTIES OF DEGENERATE P-TYPE GAAS GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-02-15)
CHEN, HD
;
FENG, MS
;
CHEN, PA
;
LIN, KC
;
WU, CC
Low-temperature (20 K) luminescent properties of heavily carbon- and zinc-doped GaAs grown by low-pressure metalorganic chemical vapor deposition were investigated. The luminescence linewidth became broader at low temperatures when p > 4 X 10(19) cm-3 due to the appearance of a shoulder peak. The main peak shifted to low energy when the dopant concentration was increased; however, the shoulder peak was at around 1.485 eV and was nearly independent of the dopant concentration. The peak of the band-to-acceptor transition occurred at low temperature and dominated the emission spectra of degenerate GaAs. The peak energy of Zn-doped samples was lower than that of C-doped samples because of the existence of defects. The excitation power intensity was varied to investigate the behavior of the shoulder peak for both types of dopants. The shoulder peak was a part of the main peak because of the recombination between the conduction band and the bottom of the impurity band.
MAGNESIUM DOPING OF INGAALP GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-09-05)
WU, CC
;
CHANG, CY
;
CHEN, PA
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CHEN, HD
;
LIN, KC
Bis(cyclopentadienyl) magnesium, CP2Mg, was used as a magnesium dopant in the InGaAlP layers by low-pressure metalorganic chemical vapor deposition. The hazy surface morphology of heavily doped InGaAlP layers is significantly improved by using magnesium dopant instead of the conventional zinc dopant. We demonstrate that the effective doping efficiency of magnesium is two orders of magnitude higher than that of zinc dopant in the heavily doped InGaAlP layer grown at 720-degrees-C.
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.
PHOTOLUMINESCENCE OF HEAVILY P-TYPE-DOPED GAAS - TEMPERATURE AND CONCENTRATION DEPENDENCES
(1994-04-01)
CHEN, HD
;
FENG, MS
;
CHEN, PA
;
LIN, KC
;
WU, JW
Photoluminescent (PL) properties of heavily carbon- and zinc-doped GaAs were investigated for concentration from 8 X 10(17) to 2.3 x 10(20) cm-3 and temperature from 300 K to 20 K. Both a band-to-band (B, B) peak and a band-to-acceptor (e, A) peak appeared at 300 K for the heavily p-type-doped GaAs PL spectra, even in degenerated GaAs. The variation of the intensities of the (e, A) peak and (B, B) peak with concentration and temperature was investigated, and the change in position of the two peaks at various concentrations and temperatures was observed. The rapid increase in linewidth with increasing concentration due to the appearance of a shoulder peak was also studied; this behavior is different from that of the shoulder peak in the PL spectrum from Zn-doped crystal.
QUANTUM CONFINEMENT EFFECTS OF SI/SIGE STRAINED-LAYER SUPERLATTICES GROWN BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION TECHNIQUE
(1994-12-01)
CHANG, TC
;
CHANG, CY
;
JUNG, TG
;
CHEN, PA
;
TSAI, WC
Well-resolved band-edge luminescence is observed for Si0.86Ge0.14/Si strained-layer superlattices grown by an ultrahigh vacuum/chemical vapour deposition technique at 550 degrees C. High-resolution double-crystal X-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (XTEM) were used to determine the strain and other parameters for these strained-layer superlattices. Quantum confinement is observed for a SiGe well as thin as 1.3 nm. The blue shift of the emission peaks with decreasing well width is found to be in good agreement with theoretical calculation.
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.