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  • 1
    Electronic Resource
    Electronic Resource
    Large, low-voltage absorption changes and absorption bistability in GaAs/AlGaAs/InGaAs asymmetric quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1972-1978 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three-step asymmetric coupled quantum wells have unique excitonic properties, particularly under bias. We demonstrate these properties through the absorption changes in quantum well optical modulators. The samples consisted of p-i-n diodes with an active region of 20 coupled wells, each coupled well containing a 50 A(ring) GaAs well and a 20 A(ring) In0.2Ga0.8As well separated by a 10 A(ring) Al0.33Ga0.67As barrier. Analysis of the structure shows that field-induced enhancement and suppression of electron and hole envelope wave function overlap can be observed through a corresponding increase or decrease in exciton absorption peaks. Our devices showed suppressed absorption with bias for the electron-heavy hole 1 exciton and enhanced absorption with bias for the electron-heavy hole 2 exciton. Stress-related effects on the electron-light hole 1 exciton are also observed. Absorption change per applied bias is five times lower than at the zero-field exciton wavelength in quantum well devices utilizing the conventional quantum-confined Stark effect (QCSE). At higher bias, the QCSE becomes dominant, producing absorptive bistability. Our devices exhibit lower chirp and lower-voltage operation than single-well devices and the flexibility of design allows for further optimization of absorption changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354756
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen passivation of nonradiative defects in InGaAs/AlxGa1−xAs quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 740-748 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of diffusion of monatomic hydrogen and deuterium in InGaAs/AlGaAs quantum wells were studied using photoluminescence (PL) and secondary-ion-mass spectroscopy. The multiquantum-well structures were grown by molecular-beam epitaxy and hydrogenated with a remote plasma. A significant increase in 77 K PL integrated intensity of bound excitons was observed after hydrogenation. This is attributed to the passivation of nonradiative recombination centers within InGaAs/AlGaAs quantum wells. A series of studies demonstrating the increase in passivation efficiency with increasing Al concentration in the barriers, the stability of the hydrogenation upon annealing to temperatures of up to and above 450 °C, the ratio of the deuterium concentration for samples with different barrier thicknesses, and the comparison of strained versus relaxed quantum wells, all strongly suggest that the passivated nonradiative recombination centers are interface defects. The stability of this hydrogen passivation at temperatures commonly used in device processing is particularly promising for device applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353331
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  • 3
    Electronic Resource
    Electronic Resource
    Low-voltage, low-chirp, absorptively bistable transmission modulators using type-IIA and type-IIB In0.3Ga0.7As/Al0.33Ga0.67As/ In0.15Ga0.85As asymmetric coupled quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6495-6502 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coupled InGaAs quantum-well systems which use field-induced spatial separation of electron and hole states to modulate the magnitude of exciton optical absorption, and hence transmission have been theoretically analyzed and experimentally demonstrated. The samples consisted of p-i-n diodes with an active region of 20 coupled wells, each coupled well containing a 50 A(ring) In0.3Ga0.7As well and a 30 A(ring) In0.15Ga0.85As well separated by a 10 A(ring) Al0.33Ga0.67As barrier. One structure was grown with the thinner well on the n-type side of each coupled quantum well while in the other sample the thinner well was oriented toward the p-type side. By applying bias to the structures, either the lowest electron or hole states effectively switch wells, thereby enhancing certain exciton resonances and quenching others. The two devices grown, despite their similar structure, operate through the field-induced switching of opposite carrier types. Because this method of modulation does not require excitons to Stark shift, the device can produce large absorption/transmission changes with zero refractive index change under bias. These first nonoptimized samples produce changes in absorption per applied bias three times larger than single-well systems. In addition, optical bistability is realizable in these structures. In addition to their presently displayed use, the coupled quantum-well structure has numerous applications for waveguide or Fabry–Perot optical modulator systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355138
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  • 4
    Electronic Resource
    Electronic Resource
    Intersubband transitions in high indium content InGaAs/AlGaAs quantum wells (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 364-366 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first observation of intersubband transitions in InyGa1−yAs(y=0.3,0.5)/ AlGaAs quantum wells. These quantum wells were grown on a GaAs substrate with a linearly graded InGaAs buffer to achieve strain relaxation before growth of the quantum wells. Measured intersubband transition energies of 316 and 350 meV are among the largest ever reported. Asymmetric step In0.5Ga0.5As/AlGaAs quantum wells designed for second harmonic generation measurements also demonstrate strong intersubband absorption at 224 meV corresponding to the 1-2 transition. With the large conduction band offsets (larger than 800 meV) available in this material system, extension to larger intersubband transitions energies for quantum well photodetector and nonlinear optics applications should be possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110044
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  • 5
    Electronic Resource
    Electronic Resource
    High contrast asymmetric Fabry–Perot electro-absorption modulator with zero phase change (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 452-454 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By analyzing the exciton line shapes of quantum wells, we can determine the wavelengths and biases at which they exhibit large absorption changes and zero refractive index changes relative to zero bias. To use this effect, we placed GaAs/AlGaAs quantum wells in the intrinsic region of a reverse-biased p-i-n diode asymmetric Fabry–Perot modulator. We then developed a sample that could be post-growth processed to optimize all relevant parameters. We used computer simulation to determine the exact post-growth correction required and produced reflection modulators with 90% reflection change and zero relative phase change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110021
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  • 6
    Electronic Resource
    Electronic Resource
    1.3 μm electroabsorption reflection modulators on GaAs (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 806-808 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a reflection electroabsorption modulator grown on a GaAs substrate operating near 1.3 μm, the dispersion minimum for silica fibers. The device was grown by molecular beam epitaxy and uses a novel technique of integrating the bottom quarter-wave mirror into a buffer with linearly graded In composition. The active area consisted of thirty InGaAs quantum wells with GaAs barriers. The mirror was formed by layers of InGaAs and InAlAs where the In concentration was graded from 0% to 35%. A maximum relative change in reflectivity, ΔR/R, of 73% at 1.33 μm was achieved. Experimental results agree with simulations performed using the transfer matrix technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109914
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxy growth of vertical cavity optical devices with in situ corrections (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1387-1389 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a novel approach to the molecular beam epitaxial (MBE) growth of vertical Fabry–Perot cavities with quarter-wave mirrors. At two selected points, the growth is interrupted and the reflectivity spectrum is measured without removing the wafer from the vacuum system. Corrections are then made in the growth of subsequent layers. By making measurements on the incomplete structure, separate corrections can be made to center both the mirror reflectivity and the cavity resonance at the desired wavelength. We present theoretical and experimental data demonstrating the effectiveness of the approach, and estimate the effects on device performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107546
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  • 8
    Electronic Resource
    Electronic Resource
    GaAs/AlAs quantum wells for electroabsorption modulators (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2779-2781 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate both theoretically and experimentally that the quantum-confined Stark effect leads to larger absorption changes in GaAs/AlAs quantum wells compared to the more conventional GaAs/AlGaAs system due to the higher Γ confinement. The lower indirect valleys in AlAs do not degrade the performance and the exciton resonance is maintained at higher-energy shifts. The improvement in exciton oscillator strength is nearly 50% with a 70-meV shift. The greater exciton strength at high fields has important applications for optical modulators and switches that operate at the long-wavelength side of the zero-bias exciton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106874
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  • 9
    Electronic Resource
    Electronic Resource
    Enhancement of photoluminescence intensity in InGaAs/AlxGa1−xAs quantum wells by hydrogenation (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2276-2278 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of diffusion of monatomic hydrogen on photoluminescence (PL) in the InGaAs/AlGaAs system has been studied. A significant increase in 77 K PL integrated intensity for In0.2Ga0.8As/AlxGa1−xAs quantum wells grown by molecular beam epitaxy is observed after hydrogenation. A 50% increase is observed for InGaAs/GaAs and the effect increases as the Al concentration increases from 0% to 33%. For 33%, the increase is approximately a factor of 9. This enhancement of the PL may be ascribed to hydrogen passivation of defects at the heterointerface or within the layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107053
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  • 10
    Electronic Resource
    Electronic Resource
    Electroabsorptive modulators in InGaAs/AlGaAs (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 888-890 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical and experimental work shows that electroabsorption improves and the quantum-confined Stark effect becomes stronger in In0.2Ga0.8As/AlxGa1−xAs quantum wells as the aluminum concentration (x) is increased in the barriers. This improved electroabsorption was used in a reflection modulator that exhibited the largest reported reflectivity change of 77%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105266
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