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ABSTRACT: 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<sup>-16</sup>–10<sup>-15</sup> cm<sup>2</sup>, 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.
Journal of Applied Physics 08/1994; · 2.17 Impact Factor
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ABSTRACT: 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 Schrödinger 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 ‖ =0. The biaxial compressive strain is observed to lower the oscillation frequency. With a nonzero wave vector (k ‖ ≠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.
Journal of Applied Physics 01/1994; · 2.17 Impact Factor
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ABSTRACT: 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
IEEE Journal of Quantum Electronics 11/1993; · 1.88 Impact Factor
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ABSTRACT: Heavily carbon‐doped GaAs (1×10<sup>18</sup>∼1×10<sup>20</sup> cm<sup>-3</sup>) grown by low‐pressure metalorganic chemical vapor deposition using triethylgallium and arsine as sources and liquid carbon‐tetrachloride (CCl 4 ) as dopant has been investigated. The carrier concentration was verified at various growth temperatures, V/III ratios, and CCl 4 flow rates. Dopant concentration first increased from 550 °C and reached a maximum at 570 °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 °C or less than 40 at T g =630 °C. Hole concentration increased and then decreased as CCl 4 flow rate increased. Growth rate of layers decreased as growth temperature and flow rate of CCl 4 increased. The doping efficiency of epitaxial layers grown on the (100) substrate was higher than that on the 2° 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 2.3×10<sup>20</sup> cm<sup>-3</sup> at T g =580 °C and V/III=10.
Journal of Applied Physics 07/1993; · 2.17 Impact Factor
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ABSTRACT: (C5H5)2Fe and Fe(CO)5 were used as the 3d transition-metal dopant sources in the growth of semi-insulating InP epitaxial layers by low-pressure metal-organic chemical vapour deposition (MOCVD). From the bright- and dark-field images of transmission electron microscopy (TEM) analysis, many precipitates were observed. Three extra peaks in the X-ray diffraction pattern were found. The peaks of band-band recombination, donor-acceptor pair recombination transitions and the recombination of donor-acceptor pair with one-phonon emission were observed in the short-wavelength range of low-temperature photoluminescence measurement. Three Fe-related peaks were observed at 0.7079, 0.6897 and 0.6683 Ev. For a wide range (10–600) of In/Fe molar fraction, the resistivity remained at high values (about 108 cm) and the highest resistivity appeared at 5 108 cm for a 1 m layer with a breakdown voltage of 9 V.
Journal of Materials Science Materials in Electronics 01/1993; 4(1):62-66. · 1.08 Impact Factor
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ABSTRACT: 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 Schrödinger 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.
Applied Physics Letters 05/1991; · 3.84 Impact Factor
