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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Electric field response of a semiconductor superlattice optical mirror from electroreflectance spectra (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1324-1326 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report low-field electroreflectance (ER) spectra of an all-semiconductor multilayer optical mirror structure. The structure, consisting of alternating blocks of AlAs/Al0.5Ga0.5 As and Al0.5Ga0.5As/GaAs multiple quantum well layers, was grown by molecular beam epitaxy without wafer rotation. Thickness variations across the wafer produce a position-dependent reflectance spectrum. The observed line shape of the band-edge exciton depends on its wavelength position relative to the mirror spectrum and cannot be explained by ordinary ER theory, due to the rapidly varying background mirror reflectance. Computer simulations, using the matrix method to calculate the reflectance for different layer thicknesses and exciton energies, agree qualitatively with the data. A strong enhancement in ER response is predicted near the minima in the mirror spectrum. This enhancement is important in electo-optic reflectance modulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101644
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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Controversy of critical layer thickness for InGaAs/GaAs strained-layer epitaxy (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 377-379 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical layer thickness for InxGa1−xAs layers in InxGa1−xAs/GaAs single strained quantum wells (SSQW's) and strained-layer superlattices (SLS's) are investigated. Photoluminescence microscopy (PLM) images and x-ray rocking curves for two series of SSQW and SLS structures corresponding to many different layer thicknesses were obtained. We find that the PLM technique, which directly images dislocations and is sensitive to low dislocation densities, is much more suitable for determining the onset of dislocation creation. The x-ray technique can detect lattice relaxation by dislocations but only at relatively high densities of dislocations. Using the former technique, we determine critical thicknesses of 190 A(ring) for SSQW's and 250 A(ring) for SLS's with x≈0.2. These results are near the theoretical predictions of J. W. Matthews, S. Mader, and T. B. Light [J. Appl. Phys. 41, 3800 (1970)] (150 and 300 A(ring), respectively) and are much lower than results obtained by x-ray or other techniques which sense lattice relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99471
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  • 9
    Electronic Resource
    Electronic Resource
    Role of experimental resolution in measurements of critical layer thickness for strained-layer epitaxy (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1080-1082 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental measurements of critical layer thicknesses (CLT's) in strained-layer epitaxy are considered. Finite experimental resolution can have a major effect on measured CLT's and can easily lead to spurious results. The theoretical approach to critical layer thicknesses of J. W. Matthews [J. Vac. Sci. Technol. 12, 126 (1975)] has been modified in a straightforward way to predict the apparent critical thickness for an experiment with finite resolution in lattice parameter. The theory has also been modified to account for the general empirical result that fewer misfit dislocations are generated than predicted by equilibrium calculation. The resulting expression is fit to recent x-ray diffraction data on InGaAs/GaAs and SiGe/Si. The results suggest that CLT's in these systems may not be significantly larger than predicted by equilibrium theory, in agreement with high-resolution measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98746
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  • 10
    Electronic Resource
    Electronic Resource
    Critical layer thickness in In0.2Ga0.8As/GaAs single strained quantum well structures (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1004-1006 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report accurate determination of the critical layer thickness (CLT) for single strained-layer epitaxy in the InGaAs/GaAs system. Our samples were molecular beam epitaxially grown, selectively doped, single quantum well structures comprising a strained In0.2Ga0.8As layer imbedded in GaAs. We determined the CLT by two sensitive techniques: Hall-effect measurements at 77 K and photoluminescence microscopy. Both techniques indicate a CLT of about 20 nm. This value is close to that determined previously (∼15 nm) for comparable strained-layer superlattices, but considerably less than the value of ∼45 nm suggested by recent x-ray rocking-curve measurements. We show by a simple calculation that photoluminescence microscopy is more than two orders of magnitude more sensitive to dislocations than x-ray diffraction. Our results re-emphasize the necessity of using high-sensitivity techniques for accurate determination of critical layer thicknesses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98984
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