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  • 1990-1994  (16)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Interfacial characteristics of AlGaAs after in situ electron cyclotron resonance plasma etching and molecular beam epitaxial regrowth (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3105-3111 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Regrown/processed AlGaAs interfaces using secondary ion mass spectrometry, cross section transmission electron microscopy (TEM), and reflection high energy electron diffraction have been characterized. Two sets of samples, GaAs/Al0.4Ga0.6As (with GaAs on top) and Al0.4Ga0.6As/GaAs (with Al0.4Ga0.6As on top), are used as starting materials. For the GaAs/Al0.4Ga0.6As samples that are first exposed to atmosphere, the experiment is performed in an integrated processing system where etching and regrowth chambers are linked together by ultrahigh vacuum transfer modules. The etching process includes electron cyclotron resonance (ECR) hydrogen plasma cleaning of GaAs native oxides, ECR SiCl4 plasma anisotropic deep etching into Al0.4Ga0.6As, and an optional, brief Cl2 chemical etching. Regrowth is carried out using solid-source molecular beam epitaxy (MBE). Despite the in situ processing, significant amounts of C, Si, and O impurities at the 10, 5, and 50×1012 cm−2 levels exist at the interfaces. However, the impurity level is one order of magnitude smaller than that in air-exposed, ECR plasma etched and MBE regrown Al0.4Ga0.6As/GaAs of the set 2 samples. As revealed using TEM, isolated small particles (presumably correlated to aluminium oxides) exist at the regrown/processed interface of the set 1 samples, but no other defects such as dislocation are seen. Impurities and defects are mainly caused by the high reactivity of AlGaAs during ECR plasma etching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356162
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    Paper (German National Licenses)
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  • 2
    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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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic properties of epitaxial single crystal ultrathin Fe3Si films on GaAs (001) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6766-6768 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic properties of Fe3Si films with thickness from 2 to 210 monolayers (ML) epitaxially grown on GaAs (001) were studied using a superconducting quantum interference device and alternating gradient force magnetometers. Growth of these single-crystal intermetallic compound films were carried out in a multichamber molecular beam epitaxy (MBE) system. The samples were covered in situ with Au 50 A(ring) thick to prevent oxidation when the samples were removed from the MBE chamber. All the films are ferromagnetic even for samples as thin as 2 ML. The easy magnetization direction of the films is parallel to the film surface. The magnetic coercivity forces (Hc) of the samples increase as the film thickness decreases to 10 ML, and then decrease when the film thickness decreases further to 2 ML.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352479
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric properties of electron-beam deposited Ga2O3 films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2715-2717 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated high quality, dielectric Ga2O3 thin films. The films with thicknesses between 40 and 4000 A(ring) were deposited by electron-beam evaporation using a single-crystal high purity Gd3Ga5O12 source. Metal-insulator-semiconductor (MIS) and metal-insulator-metal structures (MIM) were fabricated in order to determine dielectric properties, which were found to depend strongly on deposition conditions such as substrate temperature and oxygen pressure. We obtained excellent dielectric properties for films deposited at substrate temperatures of 40 °C with no excess oxygen and at 125 °C with an oxygen partial pressure of 2×10−4 Torr. Specific resistivities ρ and dc breakdown fields Em of up to 6×1013 Ω cm and 2.1 MV/cm, respectively, were measured. Static dielectric constants between 9.93 and 10.2 were determined for these films. Like in other dielectrics, the current transport mechanisms are found to be bulk rather than electrode controlled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111452
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Relative intensity noise of vertical cavity surface emitting lasers (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1194-1196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the relative intensity noise (RIN) of two all semiconductor vertical cavity surface emitting lasers is presented. We find that the slope of the low frequency RIN agrees with theory for the fundamental mode only and that transverse modes introduce sharp changes in the RIN and put a limit on the minimum attainable RIN. For the fundamental mode, both devices achieve a RIN of less than −140 dB/Hz for optical powers less than 1 mW. This good performance is attributed to the high reflectivity of the cavity mirrors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108731
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    A periodic index separate confinement heterostructure quantum well laser (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1046-1048 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel edge-emitting periodic index separate confinement heterostructure (PINSCH) semiconductor quantum well laser is proposed and demonstrated for the first time. Periodic semiconductor multilayers are used as optical confinement layers to simultaneously reduce the transverse beam divergence and increase the maximum output power. Self-aligned ridge-waveguide InGaAs/GaAs/AlGaAs PINSCH quantum well lasers emitting at 980 nm are fabricated. The 5×750 μm device has far-field angles of 10° by 20°, a threshold current of 45 mA, an external differential quantum efficiency of 1.15 mW/mA (90%), and an output power exceeding 620 mW, all measured at room temperature under CW operation. A record high fiber coupling efficiency of 51% has been achieved with a lensed fiber of 5 μm core diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106340
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    In situ growth and properties of single-crystalline-like La2−xSrxCuO4 epitaxial films by off-axis sputtering (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2748-2750 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Excellent quality La2−xSrxCuO4 epitaxial films of 0.07≤x≤0.34 in (001) and (103) orientations have been successfully grown in situ on SrTiO3, LaAlO3, and Y-stabilized ZrO2 substrates using 90° off-axis sputtering. A record low ion channeling minimal yield χmin of 1.9% is observed for the first time, and a χmin of 3% is routinely attained. The surface exhibits a featureless morphology under high-resolution scanning electron microscope, suggesting a roughness ≤30–40 A(ring). Superconductivity is maximized at Sr=0.15 with a typical Tc (R=0) of 35 K, a Jc (4.2 K) of 1–3×106 A/cm2, and a normal state resistivity two to three times lower than single crystals. Tc shows a marked reduction with thickness, and the results are interpreted on the basis of partially relieved strained-layer growth coupled with a sensitive dependence of Tc on uniaxial stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105876
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Zone lasers (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 144-146 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Vertical-cavity zone lasers (Z lasers) operating in 850 and 980 nm have been fabricated. This new class of high power, high efficiency, and large area vertical-cavity lasers has an output light that automatically comes to a focus in a single spot at a particular distance away from the laser output coupler. The light output of the 850-nm Z laser exhibits a spot size of 12 μm in the focal plane for up to several tens of mW with a 0.4-A(ring) spectral width and fixed linear polarization. Through an analysis, ways to enhance the coherence of the Z lasers will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112653
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrogen plasma removal of AlGaAs oxides before molecular beam epitaxy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 735-737 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a method for the removal of AlxGa1−xAs native oxides for 0≤x≤1, prior to molecular beam epitaxial overgrowth. The oxides formed on epilayers of AlGaAs after atmospheric exposure are removed in an electron cyclotron resonance hydrogen plasma with a substrate temperature less than 400 °C. Reflection high energy electron diffraction indicates the plasma-prepared AlGaAs surface are oxide-free and crystalline; after a vacuum anneal to 250–500 °C, GaAs or AlGaAs are epitaxially overgrown on these surfaces. Secondary ion mass spectroscopy detects C, O, and Si impurities at the interfaces, where their concentrations increase with increasing Al content of the exposed surface. The quality of the interface and the overgrown film, as observed by transmission electron microscopy, are found to be better for lower interface impurity densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108854
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  • 10
    Electronic Resource
    Electronic Resource
    Vertical microcavity surface-emitting ring laser (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2851-2852 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the performance of a novel surface-emitting laser of ring structure (RSEL). The far-field emission pattern of the RSEL remains a near-diffraction limited single lobe at 3 times the threshold current level. The structure may also be used to achieve beam width much less than that of the diffraction limit of Gaussian near-field distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106844
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