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  • Digitale Medien  (36)
  • 1990-1994  (34)
  • 1980-1984  (2)
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  • Digitale Medien  (36)
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  • 1
    Digitale Medien
    Digitale Medien
    Lateral carrier diffusion and surface recombination in InGaAs/AlGaAs quantum-well ridge-waveguide lasers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4479-4487 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We measured the increase in threshold currents due to lateral carrier diffusion in InGaAs/AlGaAs quantum-well ridge-waveguide laser diodes. The ridge stripes were fabricated by using both in situ monitored pure Cl2 reactive ion etching and selective wet etching to completely eliminate the spreading current in the conductive upper cladding layer while keeping the ridge sidewalls straight. After comparing the threshold data with a theoretical model, the ambipolar diffusion coefficient is found to be 22 cm2/s in the population-inverted InGaAs layer. This model is based on the calculated optical gain curve and the ambipolar carrier transport in the quantum-well and waveguiding layers. The dependence of carrier lifetime on the local carrier concentration is included in the calculation. Moreover, from another set of devices with the portions of the active layer outside the ridge stripes etched away, the surface recombination velocity is found to be around 1–2×105 cm/s.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357279
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  • 2
    Digitale Medien
    Digitale Medien
    High-efficiency and low-threshold InGaAs/AlGaAs quantum-well lasers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3932-3934 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High-efficiency and low-threshold InGaAs/AlGaAs quantum-well laser structures have been grown by molecular beam epitaxy. Material characterization was performed on polyimide-planarized ridge-waveguide lasers. The measured material gain data are compared to theoretical calculations that include the valence-band mixing effects. Total injection current densities of 84 and 60 A/cm2 have been measured from 50-μm-wide laser diodes with cavity lengths of 2850 μm (from a double-quantum-well sample) and 1770 μm (from a single-well sample), respectively. Moreover, we have also obtained a cw threshold current as low as 2.1 mA from a 1.7-μm-wide and 140-μm-long as-cleaved ridge-waveguide device. In addition, the lateral current leakage for the double-quantum-well sample is found to be twice that of the single-well one.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357408
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  • 3
    Digitale Medien
    Digitale Medien
    Low-temperature carrier distributions in wide quantum wells of different shapes from capacitance-voltage measurements (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1003-1007 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The carrier distributions in modulation-doped wide graded quantum wells that a measurement of the capacitance C between a surface gate and an ohmic contact to the carriers as a function of the applied bias V would yield are calculated. These capacitance-voltage (C-V) distributions are found to agree inexactly, but closely, with the calculated true carrier distributions. Density modulation features, induced by superlattices or by abrupt changes in the curvature of band-gap grading, are strikingly reproduced. Electron distributions extracted from actual measurements on a wide parabolic well and on a parabolic well with superimposed superlattice are in good agreement with theory. For the case of the parabolic well, the occupancy of a finite number of subbands is manifested as structure in the C-V distributions. This technique is relevant to the measurement of carrier distributions in any wide carrier system with more than one electric subband occupied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357886
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  • 4
    Digitale Medien
    Digitale Medien
    Electric-field-induced absorption changes in triangular quantum wells grown by pulsed-beam molecular-beam-epitaxy technique (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6461-6465 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present an observation of electric-field-induced excitonic quenching in GaAs/AlGaAs triangular quantum wells, grown by pulsed-beam molecular-beam-epitaxy technique. We have measured photocurrent spectra for both symmetric and asymmetric triangular quantum wells as a function of electric field. In both cases, at the ground-state exciton energy, we observed significant electroabsorption changes that were associated with the vanishing of sharp exciton resonances when the triangular quantum-well structures were electrically switched to systems with no quantum confinement for one or both types of carriers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345120
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  • 5
    Digitale Medien
    Digitale Medien
    Raman scattering study of InAs/GaInSb strained layer superlattices (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5608-5614 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a Raman scattering study of the InAs/GaInSb superlattice. This new superlattice is promising as a long wavelength infrared detector material. The samples were grown by molecular beam epitaxy and their structural parameters were determined by Rutherford backscattering and x-ray diffraction. Samples were grown on [001] GaAs substrates with GaSb buffers, and directly on [001] GaSb substrates. Cross-sectional transmission electron micrographs show that for the samples grown on GaAs substrates, a high density of dislocations was generated at the GaAs-GaSb interface, and many of these dislocations thread through the superlattice. The samples grown directly on GaSb had a much lower dislocation density. The Raman spectra of the InAs/GaInSb superlattice shows a single peak, which is a superposition of scattering from the LO phonons in InAs and in GaInSb. For unstrained InAs and GaInSb, the LO phonon energies are sufficiently separated that they would be well resolved in Raman scattering. However, the strain introduced into these materials by the pseudomorphic boundary conditions moves the two phonons closer together energetically so that only one peak is seen in the Raman spectrum of the superlattice. A high energy Raman scattering tail is seen in some of the samples. This tail is from Ga-As local modes. Such modes may be due to As incorporation in the GaInSb, Ga incorporation in the InAs or phase mixing at the interfaces.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.350174
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  • 6
    Digitale Medien
    Digitale Medien
    Modulation-doped graded structures: Growth and characterization (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2370-2375 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Remotely doped graded parabolic potential well structures have been grown and studied. Electrons distribute themselves uniformly in a parabolic well, the density being proportional to the curvature or quasidoping in the well. Quasidoped semiconductors are synthesized by molecular beam epitaxy in the GaAs/AlXGa1−XAs system through the digital alloy technique. The analog grading produced by the digital alloy is verified by photoluminescence excitation spectroscopy. Low temperature mobility measurements show higher mobility in these quasidoped semiconductors than in similar real-doped semiconductors. Alloy-disorder scattering is suggested to be the mobility-limiting mechanism in this digital alloy system. Capacitance–voltage profiling analysis of quasidoped semiconductors has been developed, and is used to measure carrier profiles in these structures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348720
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  • 7
    Digitale Medien
    Digitale Medien
    Terrace width evolution during step-flow growth with multiterrace adatom migration (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7351-7357 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have developed a computer-solvable model of step-flow growth that includes both anisotropic multiterrace adatom migration and asymmetric step edge attachment. We find that terrace widths equalize not only when each adatom preferentially attaches to the ascending step edge of the terrace that it lands on, but also when adatoms preferentially migrate over ascending step edges. This latter process can equalize long-range terrace width nonuniformities much more rapidly than can the former process. We also find that a slow lateral movement of terrace width distributions occurs when each adatom adheres to the step edges of the terrace that it lands on. More significantly, we find that a rapid lateral movement of terrace width distributions occurs when adatoms cross multiple step edges. This motion is especially fast when adatoms migrate distances that are comparable to or greater than the terrace width distribution period. We simulated the evolution of an experimentally observed (Al,Ga)Sb lateral superlattice (LSL) terrace width distribution, which led to quantitative estimates of the adatom migration characteristics present during the LSLs growth. At least one type of adatom, probably Ga, migrates nearly isotropically over many terraces. This method of determining adatom migration characteristics can be extended to any material system that allows LSL layers to be grown as terrace width markers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354026
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  • 8
    Digitale Medien
    Digitale Medien
    Capacitance-voltage profiling through graded heterojunctions: Theory and experiment (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 251-260 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Starting from the general equations for capacitance-voltage (CV) profiling through a graded heterojunction, we obtain numerical solutions to yield thermal-equilibrium energy-band diagrams, real electron profiles, and apparent electron profiles (i.e., the profile extracted from a CV measurement) for modulation-doped square, triangular, and parabolic potential wells. Room-temperature CV measurements are performed on parabolic potential wells grown by molecular beam epitaxy in the AlxGa1−xAs system, and the measured apparent electron profiles fitted to computer reconstructions whence the real electron distributions are deduced. These measurements reflect a uniform electron distribution in a parabolic well, with 3D electron density determined by well curvature. Data analysis also suggests the presence of a doping asymmetry in the modulation doping of the well. Appropriate corrections to growth conditions remove these asymmetries, as reflected in CV measurements. Besides its importance in the analysis of potential wells of different shapes, the theory presented is applicable to the determination of band offsets by the CV profiling technique where the unintentional grading of the band gap and/or doping in the neighborhood of the isotype abrupt heterojunction is known.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353897
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  • 9
    Digitale Medien
    Digitale Medien
    Low-threshold InGaAs/GaAs strained layer single quantum well lasers with simple ridge waveguide structure (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7892-7894 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Double heterostructure InGaAs-GaAs strained-layer single quantum well ridge waveguide lasers grown by molecular beam epitaxy were fabricated by using in situ laser monitored reactive ion etching to form the ridges. Continuous-wave threshold current as low as 3.5 mA was obtained on a ridge laser diode of 3.3 μm wide and 215 μm long having cleaved mirrors. The lasing wavelength is at 0.988 μm and the measured differential external quantum efficiency is 61%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347473
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  • 10
    Digitale Medien
    Digitale Medien
    Growth and characterization of (111) and (001) oriented MgO films on (001) GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3276-3283 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effects of substrate preparation on the structure and orientation of MgO films grown on (001) GaAs using pulsed laser deposition has been investigated. Textured MgO films displaying a (111)MgO(parallel)(001)GaAs orientation relation with x-ray rocking curve full width at half maximum (FWHM) values as low as 1.8° were obtained in cases where the native GaAs surface oxide was only partially desorbed prior to growth. Reflection high-energy electron diffraction, transmission electron microscopy (TEM), and x-ray pole figure analysis of these films reveals a preferential orientation within the plane of the substrate: [11¯0]MgO(parallel)[11¯0]GaAs and [112¯]MgO(parallel)[110]GaAs. An interfacial layer (∼5 nm thick) was observed in high resolution TEM analysis, and was attributed to a remnant native GaAs oxide layer. Complete desorption of the native GaAs oxide at ∼600 °C in vacuum prior to MgO growth led to significant surface roughening due to Langmuir evaporation, and resulted in randomly oriented polycrystalline MgO films. Growth of MgO on Sb-passivated GaAs substrates, which provided smooth, reconstructed surfaces when heated to 350 °C in vacuum, resulted in cube-on-cube oriented films [i.e., (001)MgO(parallel)(001)GaAs,[100]MgO(parallel)[100]GaAs] with x-ray rocking curve FWHM values as low as 0.47°. TEM analysis of the cube-on-cube oriented films revealed evidence of localized strain fields at the MgO/GaAs interface, indicating the presence of misfit dislocations in the MgO layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352975
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