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  • 1
    Electronic Resource
    Electronic Resource
    GaAs surface reconstruction obtained using a dry process (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2035-2037 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report attaining Ga-terminated (4×2) surface reconstruction on virgin GaAs substrates using a completely dry process at temperatures below the oxide sublimation temperature and without group V overpressure. The native oxides are removed with an electron cyclotron resonance hydrogen plasma treatment, followed by annealing at 500 °C in ultrahigh vacuum, which yields a reconstructed surface suitable for epitaxial overgrowth. Characterization by secondary ion mass spectroscopy and transmission electron microscopy reveals the complete removal of O, reduced C, and high structural order at the epilayer/substrate interface when this preparation method is used before molecular beam epitaxy. Annealing the substrate at a lower temperature yields a nonreconstructed surface possessing significant impurity concentrations, and leads to dislocation defects at the epilayer/substrate interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353148
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  • 2
    Electronic Resource
    Electronic Resource
    Wet oxidation of AlGaAs: the role of hydrogen (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 3134-3136 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wet oxidation of AlGaAs to form Al2O3 by the reduction of H+ from water to H produces intermediate As2O3. Reduction of As2O3 by H to elemental As enables the escape of arsenic from the oxidized film. Further reduction of As to AsH3 can provide another volatile As species. Formation of intermediate As is problematic for the use of wet oxidation in metal-insulator-semiconductor applications. The kinetic balance between As2O3 formation and As escape can explain the transition between the linear and parabolic time dependence of the wet oxidation of buried AlGaAs layers. The near-total suppression of wet oxidation by O2 is attributed to the suppression of volatile product formation through consumption of atomic hydrogen by reaction with O2 to form H2O in preference to the hydrogen reduction of As2O3. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366156
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  • 3
    Electronic Resource
    Electronic Resource
    Third-order optical susceptibility in short-period GaAs doping superlattices (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4387-4392 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose that short-period doping superlattices are suitable for the enhancement of a third-order susceptibility arising from free carriers in nonparabolic energy subbands. The inherent advantage lies in the ability to simply engineer the superlattice potential profile, yielding control of miniband energy dispersion. We consider short-period GaAs doping superlattices composed of uniformly doped donor and acceptor layers, and planar-doped n- and p-type monolayers separated by intrinsic regions. Calculations of the electronic structure of compensated and n-type noncompensated n-i-p-i superlattices incorporating miniband dispersion at nonzero temperature are reported. We show that small modulations of the superlattice potential lead to large subband nonparabolicities and we calculate a twentyfold improvement in the third-order susceptibility over bulk GaAs at room temperature, comparable to that predicted for GaAs/AlGaAs compositional superlattices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343933
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  • 4
    Electronic Resource
    Electronic Resource
    Tunable photoluminescence of uniformly doped short-period GaAs doping superlattices (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2805-2810 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Uniformly doped n-p GaAs doping superlattices with smaller period lengths than have been previously considered are characterized by electrochemical capacitance-voltage profiling and low-temperature photoluminescence. In spite of the short period lengths, the n-p structures exhibit obvious doping superlattice attributes. We directly observe free-carrier confinement due to the space-charge potential in superlattices with periods as short as 12 nm. The variation of the photoluminescence energy with excitation intensity decreases with reduced period lengths, while the photoluminescence intensity increases with decreasing periodicity. We observe anomalously red-shifted emission at low photoexcitation intensity in superlattices with periods of 20 nm and less. We argue that radiative recombination between spatially arranged donor and acceptor states associated to the random fluctuations in the superlattice potential occurs in superlattices with periods less than 20 nm. The occupied impurity states give rise to screening of an effective superlattice potential and the observed photoluminescence tunability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351008
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  • 5
    Electronic Resource
    Electronic Resource
    Dry lithography using focused ion beam implantation and reactive ion etching of SiO2 (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3294-3296 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a novel dry process suitable for submicron lithography using focused ion beam writing and plasma development of SiO2. Robust masks are fashioned in layers of SiO2 with a focused Ga ion beam, followed by development using CF4/O2 reactive ion etching. We find the development selectivity (etch rate ratio) between unimplanted and implanted SiO2 increases with increasing Ga dose. Using an implant dose of 1.5×1016 cm−2 we form SiO2 line and circular dot masks with dimensions as small as 300 nm. To demonstrate the utility of these durable masks, the patterns are transferred into GaAs by reactive ion etching, producing structures with aspect ratios (depth/width) greater than 10. Since masks formed of SiO2 are appropriate for ion bombardment processes such as found in plasma etching, as well as high-temperature regrowth steps, this dry lithographic technique is promising for in situ vacuum integrated fabrication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109623
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  • 6
    Electronic Resource
    Electronic Resource
    Scalability of small-aperture selectively oxidized vertical cavity lasers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 823-825 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze the threshold properties of small area selectively oxidized vertical cavity lasers. Agreement for threshold gain versus laser size is found using the experimental intrinsic threshold voltage matched with a gain theory, as compared to a two-dimensional optical cavity simulation. Our analysis indicates the increasing threshold current density of small area lasers arises from both increasing threshold gain and the concomitant increasing leakage current. We further show that the optical loss can be reduced for lasers with areas as small as 0.25 μm2 while maintaining sufficient transverse optical confinement by displacing the apertures longitudinally away from the cavity and reducing the oxide thickness. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118234
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxial regrowth on in situ plasma-etched AlAs/AlGaAs heterostructures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1738-1740 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial regrowth by solid-source molecular beam epitaxy (MBE) on dry etched heterostructures possessing exposed AlAs surfaces is accomplished for the first time using a vacuum integrated processing. Samples composed of multilayers of AlAs and AlGaAs are patterned with a SiO2 mask and are anisotropically etched using a low damage electron cyclotron resonance (ECR) SiCl4 plasma process. Etched samples are transferred in ultrahigh vacuum between the ECR and MBE chambers to avoid atmospheric exposure before regrowth. Microstructural analysis of the overgrown layers by scanning and transmission electron microscopy indicates that epitaxial regrowth on both the etched field and vertical sidewalls is achieved. The regrown material is found to contain microtwin plates, but few dislocations, indicating the good quality of the overgrowth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107202
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  • 8
    Electronic Resource
    Electronic Resource
    Selective oxidation of buried AlGaAs versus AlAs layers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1385-1387 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report significant differences between the properties of buried oxides converted from AlGaAs and AlAs layers using selective wet oxidation. Layers of AlxGa1−xAs with x≥0.96 exhibit crystallographic dependent oxidation rates, while for layers with x≤0.92 the oxidation rate is isotropic. Mesas containing partially oxidized layers of AlAs are unstable to rapid thermal cycling and exhibit excessive strain at the oxide terminus, while mesas containing partially oxidized layers of AlGaAs are robust and lack evidence of strain. Finally, the oxidation of AlGaAs layers, rather than AlAs, is found to provide robust oxide apertures for reliable vertical-cavity surface emitting lasers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117589
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  • 9
    Electronic Resource
    Electronic Resource
    Threshold investigation of oxide-confined vertical-cavity laser diodes (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3689-3691 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an experimental and theoretical analysis of the threshold properties of infrared oxide-confined vertical-cavity surface emitting lasers. We find good agreement between experiment and theory on the wavelength dependencies of the threshold current density and intrinsic voltage. The threshold voltage is shown to equal the sum of the calculated quasi-Fermi energy separation and the ohmic drop arising from a record low 17 to 30 Ω series resistance in these vertical-cavity lasers. Our analysis provides two independent means for determining the material threshold gain. A threshold gain of 500 cm−1 is found for these oxide-confined lasers, which is half that estimated for ion-implanted lasers with inferior electrical and optical confinement. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115744
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  • 10
    Electronic Resource
    Electronic Resource
    Cavity characteristics of selectively oxidized vertical-cavity lasers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3413-3415 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that a buried oxide layer forming a current aperture in an all epitaxial vertical-cavity surface emitting laser has a profound influence on the optical and electrical characteristics of the device. The lateral index variation formed around the oxide current aperture leads to a shift in the cavity resonance wavelength. The resonance wavelength under the oxide layer can thus be manipulated, independent of the as-grown cavity resonance, by adjusting the oxide layer thickness and its placement relative to the active region. In addition, the electrical confinement afforded by the oxide layer enables record low threshold current densities and threshold voltages in these lasers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113371
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