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  • 1
    Digitale Medien
    Digitale Medien
    Atomspheric pressure organometallic vapor-phase epitaxial growth and characterization of Ga0.4In0.6P/(Al0.4Ga0.6)0.5In0.5P strained quantum wells (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3356-3363 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Single and multiple Ga0.4In0.6P/(Al0.4Ga0.6)0.5In0.5P quantum wells have been grown using atmospheric pressure organometallic vapor phase epitaxy. The Ga0.4In0.6P well layers are coherently strained to match the lattice parameter of the GaAs substrate. Transmission electron microscopic results showed that the quantum-well layers are very uniform in thickness and the interface is abrupt and free of misfit dislocations. The photoluminescence peak energy increases as the well width decreases, due to carrier confinement in the quantum well. Growth interruptions do not change the photoluminescence peak energy of the quantum well. However, the photoluminescence intensity is drastically reduced for longer growth interruption times. Higher-order x-ray diffraction satellite peaks and a narrow photoluminescence halfwidth are observed in a 20-layer multiple-quantum-well sample, indicative of high structural uniformity and precise control of the composition and thickness during the growth process. Considering the effect of strain on the heterojunction band offsets, the photoluminescence peak energy of the strained quantum well can be described by a simple theory as a function of the well width.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346364
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  • 2
    Digitale Medien
    Digitale Medien
    Measurement of the fundamental band gaps of a strained GaInAs layer (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1750-1756 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: All three strain- and spin-orbit-split energy gaps of the Γ15v-Γ1c series are measured for the first time for a thin, strained Ga0.526In0.474As layer by a combination of transmission, photoreflectance (PR), and photoluminescence experiments at 10 and 300 K. Values of strain and composition of the layer are calculated from the splitting of the (J=3/2, mj=±3/2) and (3/2, ±1/2) valence bands and from x-ray data. Force balance calculations predict the strain in the layer to be relaxed while energy balance calculations predict the layer to be strained. The onset of generation of misfit dislocations at the InP/GaInAs interface has recently been reported to be well described by the force balance model. Nevertheless, the data reported in the present study show the degree of plastic strain relaxation for the sample under investigation to be so small that it can be neglected for the interpretation of the optical spectra. Almost identical PR spectra are measured when the sample is excited at photon energies larger and smaller than the InP band gap. In both cases, the PR signal originates from modulation of built in fields at the heterointerfaces, rather than the surface field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346604
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  • 3
    Digitale Medien
    Digitale Medien
    Investigation of reactive-ion-etch-induced damage of InP/InGaAs multiple quantum wells by photoluminescence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1528-1532 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effects of CH4/H2 reactive ion etching (RIE) on the optical properties of an InP/InGaAs multiple-quantum-well structure have been investigated by low-temperature photoluminescence (PL). The structure consisted of eight InGaAs quantum wells, lattice matched to InP, with nominal thicknesses of 0.5, 1, 2, 3, 5, 10, 20, and 70 monolayers, respectively, on top of a 200-nm-thick layer of InGaAs for calibration. The design of this structure allowed etch-induced damage depth to be obtained from the PL spectra due to the different confinement energies of the quantum wells. The samples showed no significant decrease of luminescence intensity after RIE. However, the observed shift and broadening of the PL peaks from the quantum wells indicate that intermixing of well and barrier material increased with etch time. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360245
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  • 4
    Digitale Medien
    Digitale Medien
    Terahertz radiation from delta-doped GaAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 79-81 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Terahertz pulse emission from four different delta-doped molecular beam epitaxially grown GaAs samples is studied. We observe a decrease of the emitted THz pulse amplitude as the distance of the delta-doped layer from the surface is increased, and a change in polarity of the THz pulses as compared to bulk n-type doped GaAs reference samples. The electric fields in the region of the doping layer are investigated by photoreflectance spectroscopy. A careful analysis of Franz–Keldysh oscillations observed in the photoreflectance spectra provides information about the built-in fields on both sides of the delta-doped layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.113080
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  • 5
    Digitale Medien
    Digitale Medien
    Femtosecond dynamics and absorbance of self-organized InAs quantum dots emitting near 1.3 μm at room temperature (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2201-2203 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High-sensitivity, femtosecond differential transmission measurements on self-organized InAs quantum dots at room temperature allow us to determine the dynamics of resonantly excited electron-hole pairs, as well as the absorbance (α0d) of quantum dots. The room temperature differential transmission signal decreases with a time constant of 65 ps, determined by the rate of excitation from the initial photoexcited states to higher excited states. From the magnitude of the differential transmission, we deduce that the absorbance, and hence the maximum gain/pass in the direction normal to the layers, is (approximate)2.1×10−3 at the spectral peak for our sample with six layers of quantum dots. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1315347
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  • 6
    Digitale Medien
    Digitale Medien
    GaInP/AlGaInP strained quantum wells grown using atmospheric pressure organometallic vapor phase epitaxy
    Amsterdam : Elsevier
    Journal of Crystal Growth 109 (1991), S. 279-284 
    Details
    ISSN: 0022-0248
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-0248(91)90191-7
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  • 7
    Digitale Medien
    Digitale Medien
    Interwell excitons in GaAs multiple quantum wells and superlattices (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1359-1366 
    Details
    ISSN: 0392-6737
    Schlagwort(e): Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical mutation) ; Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Weak localization effects (e.g., quantized states) ; Conference proceedings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary The optical properties of multiple quantum wells in the transition from isolated wells to a superlattice are investigated theoretically and experimentally. For superlattices with a miniband width similar to the binding energy of the 2s exciton of the isolated quantum well we find an exciton state energetically between the 1s exciton state and the onset of the miniband absorption. We find this state to be an interwell exciton, with the electron confined to one well and the hole to the neighboring well. The interwell exciton resembles the first Wannier-Stark localized exciton of a biased superlattice. However, the localization in the present case is mediated by the Coulomb interaction of the electron and hole. The state has considerable oscillator strength and is observed experimentally in linear and nonlinear experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02457210
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  • 8
    Digitale Medien
    Digitale Medien
    Direct and spatially indirect excitons in GaAs/AlGaAs superlattices in strong magnetic fields (1998)
    Springer
    Physics of the solid state 40 (1998), S. 767-769 
    Details
    ISSN: 1063-7834
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Luminescence and luminescence excitation spectra are used to study the energy spectrum and binding energies of direct and spatially indirect excitons in GaAs/AlGaAs superlattices having different electron and hole miniband widths in high magnetic fields perpendicular to the heterolayers. The ground state of the indirect excitons formed by electrons and holes which are spatially distributed among neighboring quantum wells is found to lie between the ground 1s state of the direct excitons and the threshold of the continuum of dissociated exciton states in the minibands. The indirect excitons have a substantial oscillator strength when the binding energy of the exciton exceeds the scale of the width of the resulting miniband. It is shown that a high magnetic field shifts a system of symmetrically bound quantum wells toward weaker bonding. At high exciton concentrations, spatially indirect excitons are converted into direct excitons through exciton-exciton collisions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.1130446
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  • 9
    Digitale Medien
    Digitale Medien
    Direct and spatially indirect excitons in GaAs/AlGaAs superlattices in strong magnetic fields (1997)
    Springer
    Journal of experimental and theoretical physics 85 (1997), S. 601-608 
    Details
    ISSN: 1090-6509
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Luminescence and luminescence excitation spectra are used to study the energy spectrum and binding energies of direct and spatially indirect excitons in GaAs/AlaAs superlattices, with different widths of the electron and hole minibands, located in a high magnetic field perpendicular to the heterolayers. It is found that the ground state of the indirect excitons formed by electrons and holes and spatially separated between neighboring quantum wells lies between the ls ground state of the direct excitons and the continuum threshold for dissociated exciton states in the minibands. Indirect excitons in superlattices have a significant oscillator strength when the binding energy of the exciton exceeds the order of the width of the resulting miniband. The behavior of the binding energy of direct and indirect heavy hole excitons during changes in the tunneling coupling between the quantum wells is established. It is shown that a strong magnetic field, which intensifies the Coulomb interaction between the electron and hole in an exciton, weakens the bond in a system of symmetrically bound quantum wells. The spatially indirect excitons studied here are analogous to first order Wannier-Stark localized excitons in superlattices with inclined bands (when an electrical bias is applied), but in the present case the localization is of purely Coulomb origin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.558344
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  • 10
    Digitale Medien
    Digitale Medien
    Exciton-exciton collisions and conversion of interwell excitons in GaAs/AlGaAs superlattices (1997)
    Springer
    JETP letters 65 (1997), S. 656-662 
    Details
    ISSN: 1090-6487
    Schlagwort(e): 71.35.Gg ; 78.47.+p
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The ratio of the densities of intra-and interwell excitons in a symmetric system of coupled quantum wells — a superlattice based on a GaAs/AlGaAs heterostructure — is investigated over a wide range of optical excitation power densities. Conversion of interwell excitons into intrawell excitons as a result of exciton-exciton collisions is observed at high exciton densities. Direct evidence for such a conversion mechanism is the square-root dependence of the interwell exciton density on the optical excitation level. The decrease in the lifetime of interwell excitons with increasing excitation density, as measured directly by time-resolved spectroscopy methods, confirms the explanation proposed for the effect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.567402
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