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  • 1
    Electronic Resource
    Electronic Resource
    Time-resolved carrier recombination dynamics of 1.3–1.8 μm broadband light emitting diode structures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6965-6971 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a time-resolved study of carrier recombination dynamics of broadband light emitting diode structures comprised of a series of InGaAs/InGaAlAs digital pseudoalloy short period superlattices fabricated by molecular beam epitaxy. The structure consists of three quantum wells equally spaced in emission energy over the 1.3–1.8 μm range. We performed a time-resolved study of carrier recombination process for each quantum well using optical pumping. Experimental results show that carrier tunneling across adjacent wells plays a major role in the overall carrier population distribution across the three wells. By tailoring the thicknesses of barriers and wells of the structure, uniform spectral emission covering 1.3–1.8 μm range can be achieved. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363769
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  • 2
    Electronic Resource
    Electronic Resource
    X-ray reciprocal-space mapping of strain relaxation and tilting in linearly graded InAlAs buffers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3578-3584 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The extent of relaxation and orientation of linearly graded InxAl1-xAs (x=0.05–0.25) buffers grown on GaAs were examined using a novel x-ray diffraction reciprocal-space mapping technique (kmap). Samples were grown at temperatures ranging from 370 to 550 °C. The fractional relaxation of the buffers grown between 470 and 550 °C was essentially identical (77%) and symmetric in orthogonal 〈110〉 directions. These buffers are believed to be in equilibrium indicating that the incomplete relaxation is not a kinetic effect. The extent of relaxation was less than that expected for equilibrium relaxation in the absence of dislocation–dislocation interactions indicating that such interactions must be considered to accurately predict the extent of relaxation. The saturation of the relaxation as a function of temperature indicates that at the grading rate used (8% In/μm or 0.69% strain/μm), we are not working in a growth regime where the relaxation is nucleation limited. In addition, all the buffers are slightly tilted with respect to the GaAs substrate about [11¯0] toward the [110] direction suggesting either a bias in the dislocation types in the boule-grown GaAs, or a bias in the way in which α and β dislocations interact with unintentional substrate miscuts. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361410
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  • 3
    Electronic Resource
    Electronic Resource
    Zinc-implantation-disordered (InGa)As/GaAs strained-layer superlattice diodes (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1131-1134 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have examined the properties of (InGa)As/GaAs strained-layer superlattices (SLSs) that have been disordered by implantation of 5×1015/cm2, 250 keV 64Zn+ followed by controlled atmosphere annealing at 680 °C for 30 min. Ion channeling techniques indicate that the Zn-disordered regions of the SLS contain extensive crystalline damage after annealing. Simulations of the disordering process using an analytic ion range code predict that the electrical junction resulting from the implantation process is located outside the disordered region of the SLS in both the vertical and the lateral directions. Junction electroluminescence intensity for given drive current densities from the Zn-disordered SLS devices is comparable to that from reference Be-implantation-doped (SLS retained) devices and greatly exceeds that from heavily dislocated grown-junction mesa diodes in the homogeneous alloy of the average SLS composition; this result is consistent with the results of the simulations. This study demonstrates that implantation disordering can be as useful for strained-layer systems as for less severely mismatched heterojunction systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337356
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  • 4
    Electronic Resource
    Electronic Resource
    Energy levels of finite-depth quantum wells in an electric field (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2273-2276 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical calculations of energy levels and wavefunctions for a particle in a finite quantum well subject to an electric field are described. The calculations are restricted to the regime where the tunneling rate out of the well is small. In this regime the results are in good agreement with results of an approximate calculation wherein the finite well is replaced by an infinitely deep well whose width has been adjusted (separately for each level) to obtain the correct zero-field eigenvalue, as recently proposed for the ground state by Miller et al. [D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard, W. Wiegmann, T. H. Wood, and C. A. Burrus, Phys. Rev. B 32, 1043 (1985)]. Over a significant range of well depths and fields (which are the only variables, provided that appropriately normalized units are used), it is found that the difference between the approximate and exact eigenvalues can be accurately estimated from a simple empirical formula. These results should be useful in studies of electro-optic effects in semiconductor quantum-well structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337989
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of ion-implantation doping of strained-layer superlattices. II. Optical and electrical properties (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3641-3650 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the properties of Ga(AsP)/GaP strained-layer superlattices (SLSs) that have been doped by implantation of 1×1015/cm2, 75 keV Be+ followed by controlled-atmosphere annealing at 825 °C for 10 min. Our results indicate that doping of these strained-layer superlattices without disordering is a viable process. Liquid-helium temperature photoluminescence suggests a binding energy for the implanted acceptors of 50 meV, consistent with that of beryllium in GaP-based alloys. The implantation-doped regions exhibit room-temperature electrical activation of 15% and hole mobilities of 20 cm2/V s, consistent with the values expected for type-converted GaP-based alloys. SLS diodes fabricated by this process exhibit excellent rectification properties, with a forward turn-on voltage of approximately 1.8 V and low values of room-temperature reverse leakage current densities. Diodes formed from SLSs with original n-type doping of 1×1017/cm3 have typical reverse leakage current densities of 1×10−7 A/cm2 at −10 V, despite the depletion region penetrating approximately ten interfaces of the SLS at this bias. Deep-level transient spectroscopy demonstrates the existence of defect centers, whose densities and signatures are similar to those found in ion-implanted GaP. The implanted photodiodes exhibit a wavelength-dependent photoresponse characteristic of grown-junction SLS photodetectors in the same chemical system. Examination of the spatial response of the photodiodes to a tightly focussed (FWHM=2.45 μm) laser beam at a wavelength of 488 nm indicates that the photoresponse from the device is uniform to within 10% for regions away from the edges of the implanted regions. Modelling of the wavelength-dependent and the spatially dependent photoresponse allows an estimate of minority-carrier diffusion lengths for electrons and holes of 1.0 μm parallel to the SLS layers and 0.1 μm perpendicular to the SLS layers. The excellent electrical and optical properties of the implanted and annealed SLS materials implies additional device applications for these novel materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337796
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  • 6
    Electronic Resource
    Electronic Resource
    Graded-composition buffer layers using digital AlGaAsSb alloys (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2320-2322 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe step-graded digital-alloy buffers using alternate layers of Al0.5Ga0.5As and Al0.5Ga0.5As0.65Sb0.35 grown on GaAs substrates by molecular beam epitaxy. The buffers consist of three sets of superlattices with AlGaAs/AlGaAsSb layer thicknesses of 7.7/2.3 nm, 5.4/4.6 nm, and 3.1/6.9 nm, respectively, terminating in a lattice constant equal to that of bulk In0.32Ga0.68As. Transmission electron micrographs show that most of the misfit-generated dislocations lie near the steps in pseudoalloy composition, and atomic force micrographs indicate a rms surface roughness of 3.6 nm. A 20.5-period lattice-matched InGaAs/InAlAs reflector stack grown on such a buffer has a peak reflectivity of 98% near 1.3 μm. These buffers provide potentially useful substrates for optoelectronic device applications near 1.3 μm using strained InGaAs active regions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114331
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  • 7
    Electronic Resource
    Electronic Resource
    Novel reflectance modulator employing an InGaAs/AlGaAs strained-layer superlattice Fabry–Perot cavity with unstrained InGaAs/InAlAs mirrors (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1608-1610 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a novel approach to optoelectronic devices by combining mechanically stable strained and unstrained epitaxial multilayers. We illustrate our approach with an optical reflectance modulator based on an asymmetric Fabry–Perot resonator designed to operate near 1.06 μm. The resonator is grown on a mechanically relaxed buffer of In0.11Ga0.89As deposited on a GaAs substrate. For mirrors, quarter-wave stacks of In0.11Ga0.89As and In0.1Al0.9As, lattice matched to the buffer, are used. The Fabry–Perot cavity consists of an In0.23Ga0.77As/Al0.35Ga0.65As strained-layer superlattice whose planar lattice constant also matches the buffer. Our first device operates at 1.04–1.05 μm depending on lateral position across the wafer. The insertion loss at resonance is less than 2 db and a fractional modulation of over 60% has been achieved with a 4 V bias swing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105140
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  • 8
    Electronic Resource
    Electronic Resource
    Electric field dependent photocurrent and electroreflectance spectra of InGaAs/AlGaAs multiple strained quantum well structures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1245-1247 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results on excitonic transitions and confinement at high electric fields from photocurrent and electroreflectance spectra of an In0.17Ga0.83As/Al0.3Ga0.7As strained quantum well structure fabricated into a Schottky barrier diode. Up to the highest field attained, 1.7×105 V/cm, we observe a well-defined exciton line at the band edge (in contrast to data on similar GaAs/Al0.3Ga0.7As structures), a feature important for potential optoelectronic applications. At low fields, "allowed'' (Δn=0) transitions dominate the photocurrent spectra, but with increasing field "forbidden'' transitions (allowed because of reduced symmetry and valence-band mixing) grow in intensity and eventually dominate the above-gap response. In the electroreflectance spectra, the forbidden transitions are relatively strong, even at low field. The allowed above-gap transitions nearly vanish at low temperature because of the small field dependence of the higher lying quantum well energy levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103498
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of energy-band dispersion curves in strained-layer structures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2227-2229 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simultaneous measurement of both the conduction- and valence-band dispersion curves in single strained-layer structures is presented. These measurements rely on the application of recent observations regarding breaking of the usual selection rules for interband magnetoluminescence transitions in modulation-doped structures. Low-temperature magneto-luminescence data for three representative InGaAs/GaAs n-type single-strained quantum well structures are presented. For energies approaching 50 meV above the band gap, we find that the conduction band is parabolic with an effective mass of 0.071m0. Over the same energy range, the valence bands are highly nonparabolic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101367
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  • 10
    Electronic Resource
    Electronic Resource
    Electrical and optical studies of dislocation filtering in InGaAs/GaAs strained-layer superlattices (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1098-1100 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report electrical transport and optical studies of the efficiency with which an In0.2Ga0.8As/GaAs strained-layer superlattice (SLS) can filter threading dislocations generated in a thick In0.1 Ga0.9 As layer grown on GaAs. The electrical studies, the first of their kind, rely on a novel test structure which allows electrical characterization of just the top portion of the SLS, with the bottom portion acting as the dislocation filter. For optical characterization we detect dislocations directly by photoluminescence microscopy. The electrical results show that ∼3–6 periods of filtering are needed to attain high mobilities. The photoluminescence microimages show a small density of dislocations near the top of an eight-period SLS but no dislocations for 11 or more periods. Filtering with In0.2Ga0.8As/GaAs SLS's is more effective than with GaAs0.8P0.2/GaAs SLS's, possibly because of larger interlayer differences in strain and elastic constants for the former.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100032
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