ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Large, low-voltage absorption changes and absorption bistability in GaAs/AlGaAs/InGaAs asymmetric quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1972-1978 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three-step asymmetric coupled quantum wells have unique excitonic properties, particularly under bias. We demonstrate these properties through the absorption changes in quantum well optical modulators. The samples consisted of p-i-n diodes with an active region of 20 coupled wells, each coupled well containing a 50 A(ring) GaAs well and a 20 A(ring) In0.2Ga0.8As well separated by a 10 A(ring) Al0.33Ga0.67As barrier. Analysis of the structure shows that field-induced enhancement and suppression of electron and hole envelope wave function overlap can be observed through a corresponding increase or decrease in exciton absorption peaks. Our devices showed suppressed absorption with bias for the electron-heavy hole 1 exciton and enhanced absorption with bias for the electron-heavy hole 2 exciton. Stress-related effects on the electron-light hole 1 exciton are also observed. Absorption change per applied bias is five times lower than at the zero-field exciton wavelength in quantum well devices utilizing the conventional quantum-confined Stark effect (QCSE). At higher bias, the QCSE becomes dominant, producing absorptive bistability. Our devices exhibit lower chirp and lower-voltage operation than single-well devices and the flexibility of design allows for further optimization of absorption changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354756
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen passivation of nonradiative defects in InGaAs/AlxGa1−xAs quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 740-748 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of diffusion of monatomic hydrogen and deuterium in InGaAs/AlGaAs quantum wells were studied using photoluminescence (PL) and secondary-ion-mass spectroscopy. The multiquantum-well structures were grown by molecular-beam epitaxy and hydrogenated with a remote plasma. A significant increase in 77 K PL integrated intensity of bound excitons was observed after hydrogenation. This is attributed to the passivation of nonradiative recombination centers within InGaAs/AlGaAs quantum wells. A series of studies demonstrating the increase in passivation efficiency with increasing Al concentration in the barriers, the stability of the hydrogenation upon annealing to temperatures of up to and above 450 °C, the ratio of the deuterium concentration for samples with different barrier thicknesses, and the comparison of strained versus relaxed quantum wells, all strongly suggest that the passivated nonradiative recombination centers are interface defects. The stability of this hydrogen passivation at temperatures commonly used in device processing is particularly promising for device applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353331
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Effect of high current density and doping concentration on the characteristics of GaAs/AlAs vertically integrated resonant tunneling diodes (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7141-7148 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of high current density and doping concentration on the current-voltage (I-V) characteristics of vertically integrated resonant tunneling diodes (VIRTDs) is experimentally determined. Room-temperature peak current densities as high as 2.7×104 A/cm2 and first and second peak-to-valley ratios of 3.6 and 2, respectively, are achieved in VIRTDs with 6-monolayer (ML) (17 A(ring)) barrier RTDs and 600 A(ring) separation between them. Symptoms of degradation in the I-V characteristics of these devices, which are attributed to insufficient longitudinal momentum relaxation in the region between RTDs, turn into a serious problem when the separation between RTDs is decreased to 500 A(ring). Through the variation of doping in the separation region, higher doping (3×1018 cm−3) between RTDs is proposed to remedy this problem and demonstrated to be quite effective in restoring the I-V characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349798
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Zero chirp quantum well asymmetric Fabry–Perot reflection modulators operating beyond the matching condition (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7061-7066 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate asymmetric Fabry–Perot reflection modulators using both InGaAs and GaAs quantum wells which operate beyond the matching condition and exhibit zero phase change (zero chirp) when switched. These devices are structurally similar to devices which can operate before the matching condition, and with incorporation of only a small etch step enable planar realization of zero phase change modulators operating before and beyond the matching condition which reflect 180° out of phase. We also show how observation of the reflectivity spectrum can provide quick information about the voltage necessary to obtain this zero chirp behavior. These structures provide a basis for low chirp optical switching, beam steering, and spatial light modulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355020
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Low-voltage, low-chirp, absorptively bistable transmission modulators using type-IIA and type-IIB In0.3Ga0.7As/Al0.33Ga0.67As/ In0.15Ga0.85As asymmetric coupled quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6495-6502 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coupled InGaAs quantum-well systems which use field-induced spatial separation of electron and hole states to modulate the magnitude of exciton optical absorption, and hence transmission have been theoretically analyzed and experimentally demonstrated. The samples consisted of p-i-n diodes with an active region of 20 coupled wells, each coupled well containing a 50 A(ring) In0.3Ga0.7As well and a 30 A(ring) In0.15Ga0.85As well separated by a 10 A(ring) Al0.33Ga0.67As barrier. One structure was grown with the thinner well on the n-type side of each coupled quantum well while in the other sample the thinner well was oriented toward the p-type side. By applying bias to the structures, either the lowest electron or hole states effectively switch wells, thereby enhancing certain exciton resonances and quenching others. The two devices grown, despite their similar structure, operate through the field-induced switching of opposite carrier types. Because this method of modulation does not require excitons to Stark shift, the device can produce large absorption/transmission changes with zero refractive index change under bias. These first nonoptimized samples produce changes in absorption per applied bias three times larger than single-well systems. In addition, optical bistability is realizable in these structures. In addition to their presently displayed use, the coupled quantum-well structure has numerous applications for waveguide or Fabry–Perot optical modulator systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355138
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Creation and optimization of vertical cavity phase flip modulators (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4878-4884 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The creation of vertical cavity phase flip modulators is demonstrated, both theoretically and experimentally. These modulators rely on both the ability to make Fabry–Pérot cavities which switch the dominant mirror responsible for reflection and the use of excitons in a manner which allows them to provide large absorption changes with zero parasitic refractive index changes. The current device provides a 180° phase change while only changing reflectivity from 65% to 63% with an applied bias of 13.5 V while using an active region only 5000 A(ring) long. These devices can be placed into dense arrays and should have numerous applications for stackable optical switching and logic, high-efficiency spatial light modulation, and, with appropriate optimization, low-reflectivity-change analog phase modulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355773
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The use of graded InGaAs layers and patterned substrates to remove threading dislocations from GaAs on Si (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2697-2702 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated threading dislocation (TD) removal from GaAs films on Si by introduction of additional InGaAs graded strain layers in combination with growth on patterned substrates. The substrate patterns consisted of mesas with 10–34 μm widths. The mesa sidewalls were either overhanging (concave), leading to free sidewalls for the film on the mesas, or outward sloping (convex) sidewalls with {111} orientation. The dislocation structure was studied using transmission electron microscopy. It was found that the graded strained layers led to a reduction of dislocation density by a factor of ∼5 in films grown both on mesas with concave sidewalls and on unpatterned substrates. This reduction was due to dislocation reactions leading to annihilation of TDs. For films with graded strained layers on mesas with convex sidewalls, an additional factor of ∼3 reduction in TD density was observed in the part of the film that was grown on top of the mesas. In this case all mobile TDs (TDs associated with 60° misfit dislocations, i.e., TDs that could glide to relieve misfit stress) were removed from the film on top of the mesas to the regions above the sidewalls and only TDs associated with 90° misfit dislocations remained. We suggest that this is due to pinning of the TDs associated with 60° misfit dislocations at the mesa edges and we have presented an explanation for this pinning in terms of the stress conditions at the {111} oriented mesa edges. In addition, this leads us to suggest that in order to obtain minimum TD density it is imperative to prevent formation of 90° misfit dislocation during lattice mismatched heteroepitaxial growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357572
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Novel cavity design for high reflectivity changes in a normally off electroabsorption modulator (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 813-815 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate both theoretically and experimentally a novel Fabry–Perot electroabsorption modulator. Both a normally off reflectivity characteristic and negative differential conductivity were obtained by increasing the optical absorption coefficient with voltage. Using the large absorption change of the quantum confined Stark effect, we obtain excellent modulation characteristics with a change in absolute reflectivity of 47% and a contrast ratio greater than 15.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104497
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Atomically layered heteroepitaxial growth of single-crystal films of superconducting Bi2Sr2Ca2Cu3Ox (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 931-933 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic layering of high-temperature superconducting compounds has been employed to grow films of Bi2Sr2Ca2Cu3Ox, in situ, on SrTiO3 substrates. Atomic monolayers of the constituent atoms were sequentially deposited by shuttering the fluxes from thermal effusion cells, and oxidation of the film was accomplished using a beam of ozone. The films were superconducting as-grown, with complete resistive transitions as high as 86 K. Moreover, reflection high-energy electron diffraction patterns observed during growth, as well as post-growth analysis by x-ray diffraction and high-resolution scanning electron micrography, indicate the films to be single crystal and heteroepitaxial, with in-plane a-b twinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104270
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Second-order susceptibility in asymmetric quantum wells and its control by proton bombardment (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1724-1726 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of extremely large mid-infrared second-order susceptibilities due to intersubband transitions in an asymmetric quantum well, and selective suppression of these susceptibilities by proton bombardment of the sample. The measured second-order susceptibility for second-harmonic generation of 9.25–10.78 μm is in good agreement with theoretical calculations based on measured infrared absorption spectra, which show the lowest two intersubband transitions. The peak value of the susceptibility is 58 nm/V, 320 times larger than the bulk nonlinear susceptibility of GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105121
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...