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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 97-103 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage produced at the interfaces in a sample of GaAs/Al0.6Ga0.4As/GaAs that has been subjected to ion implantation at 77 and 293 K with 1 MeV Kr+ ions has been investigated using a combination of ion channeling and transmission electron microscopy (TEM) techniques. Low temperature ion-channeling spectra obtained from samples implanted at 77 K, to an ion dose of 1014 ions cm−2, were similar to the random spectrum, indicating that the GaAs and Al0.6Ga0.4As layers had sustained a considerable degree of damage. An asymmetric signal developed in the He+ ion-channeling spectrum as the sample warmed to room temperature. The backscattering yield corresponding to the bottom interface (i.e., Al0.6Ga0.4As grown on GaAs) resembled that of the random yield, whereas that from the top interface (GaAs grown on Al0.6Ga0.4As) decreased, shifting toward the unirradiated channeled spectrum. This observation suggests that the damage produced near the top of the Al0.6Ga0.4As layer is thermally unstable. Cross-sectional TEM images reveal a greater amount of damage in the form of extended defects and amorphous regions at the bottom interface than at the top one. This difference is sufficient to account for the observed asymmetry in the channeling spectra. Increasing the ion dose to 1015 ions cm−2 produced a damage state throughout the Al0.6Ga0.4As layer that was stable at both 77 and 293 K. TEM examination revealed that at this ion dose the GaAs and Al0.6Ga0.4As layers were both amorphous. Room-temperature implantation to a dose of 1×1016 ions cm−2 was also performed. Planar defects were observed at both interfaces, although their density appeared to be greater near the bottom interface.In addition, the bottom interface was rougher than the top. The difference in the damage states at the bottom and top interfaces can be attributed to a variation in the number of displacement cascade events as a function of depth through the Al0.6Ga0.4As layer. This variation in the number of cascades results in different amounts of ion mixing at the top and bottom interfaces. © 1995 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4366-4371 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To determine the influence of interface type on the accumulation of damage and ion mixing in GaAs/AlxGa1−xAs heterostructures, the damage produced by ion implantation at 77 K in single-layer (GaAs/AlxGa1−xAs/GaAs) and double-layer (GaAs/AlxGa1−xAs/GaAs/ AlxGa1−xAs/GaAs) heterostructures has been investigated by using a combination of Rutherford backscattering spectrometry and transmission electron microscopy. In the single-layer geometry, the degree of disorder increases with depth and the mixing is greater at the AlxGa1−xAs on GaAs interface than at the GaAs on AlxGa1−xAs one. The damage distribution in the sample with the double-layer geometry was different in the two layers, but overall it was similar to that in the single-layer geometry. These trends were observed in samples with x=0.6 and 0.2. These results indicate that migration of charged defects due to the presence of an implantation-induced electric field is not responsible for the asymmetry in the damage accumulation across the layer, the interface disorder and ion mixing, and the initiation of amorphization at interfaces. Instead, these effects can be better understood in terms of the depth dependence of the density of cascade events. © 1996 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3543-3545 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion-beam mixing in AlxGa1−xAs and InP matrices was measured as a function of irradiation temperature using 1 MeV Kr ion irradiation. For these III–V compound semiconductors, the mixing increased with temperature up to a critical temperature Tc at which point it precipitously dropped. Tc was identified as the amorphous-to-crystalline transition temperature in these materials under 1 MeV Kr irradiation. © 1995 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 4209-4211 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report monolayer-by-monolayer epitaxy of GaAs at 650 °C using surface photoabsorption (SPA) to monitor growth. Our results show, as confirmed by photoluminescence measurements, the possibility of growing highly accurate quantum well heterostructures by metal–organic chemical-vapor deposition at conventional growth temperatures. In addition, we observe a continuous increase of the SPA signal during trimethylgallium exposure that cannot be explained by present growth models. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3847-3849 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Annealed and nonannealed p-contact metallization for asymmetric cladding separate confinement heterostructure lasers with a thin p-cladding layer is reported. Ti–Au and annealed Ti–Pt–Au p-type contacts are demonstrated to improve the adhesion over a pure gold contact and allow annealing of the metallization to thin p-cladding laser structures at the expense of an increase in the optical loss. The increased optical loss is due to the decreased conductivity of titanium and platinum as compared to gold. As little as 10 A(ring) of titanium is adequate for an adhesion layer and only increases the optical loss by 1.6 cm −1 over a pure gold metallization which has an optical loss of 10.0 cm−1. A metallization of 15 A(ring) Ti−15 A(ring) Pt−1500 A(ring) Au is adequate for an anneal at 410 °C for 10 s and increases the optical loss by 7.0 cm −1. © 1995 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1265-1269 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction and channeling-Rutherford backscattering spectrometry (RBS) were employed to investigate damage accumulation in AlxGa1−xAs (x=0.50, 0.75, 0.85, and 1.0) irradiated at 80 K with MeV ions. The x-ray measurements, performed both before and after warming the samples, showed a transition in the strain accumulation behavior as the Al content increased. For samples with low Al content, x=0.50, the strain increased monotonically with fluence until the sample amorphized, a behavior similar to GaAs. For samples with x≥0.75, the strain initially increased, then plateaued, and finally diminished at high fluences. The RBS data, obtained at both 80 K and room temperature, revealed a similar dependence of the amorphization behavior upon Al content. For pure AlAs films, amorphization in the bulk was not observed even after a fluence of 2×1017 cm2 of 1.7 MeV Ar+. For films with low Al content, however, the AlxGa1−xAs layer readily amorphized with a fluence of only 6.8×1014 cm2 of 1.7 MeV Ar+. From these data, along with previously published information provided by transmission electron microscopy studies, a model for damage accumulation in ion irradiated AlxGa1−xAs is proposed. © 1998 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 820-822 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented for single longitudinal mode, strained-layer AlGaAs-GaAs-InGaAs quantum well heterostructure distributed feedback lasers emitting near 980 nm. Device fabrication consists of conventional holographic photolithography and two-step metalorganic chemical vapor deposition growth. Regrowth over a GaAs grating layer and GaAs solid phase mass transport are discussed. The lasers are single mode up to twice Ith, have differential quantum efficiencies of 50%, and have threshold current densities of 600 A/cm2.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2123-2125 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed photoluminescence measurements probing the strain in a set of In0.10Ga0.90As/GaAs multiquantum well (MQW) samples. By using different continuous wave pump laser wavelengths we obtain a depth profile of strain in individual quantum wells within the MQW structure. We also present evidence for the existence of an equilibrium strain between In0.10Ga0.90As quantum well layers and GaAs barrier layers for thick strain-relaxed MQW structures.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 421-423 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation-induced damage and strain in AlAs were investigated by measurements of the lattice parameter using x-ray diffraction. Irradiations employed MeV C, Ar, and Au ion beams at 25 or 80 K. The out-of-plane lattice parameter increased with fluence at low doses, saturated, and then decreased to nearly its original value. The in-plane lattice parameter did not change, throughout. These results were independent of the irradiation particle when scaled by damage energy. Selected samples were examined by high-resolution and conventional transmission electron microscopy. Recovery of the lattice parameter during subsequent thermal annealing was also investigated.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 976-978 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion beam mixing of AlAs markers in GaAs and GaAs markers in AlAs has been measured as a function of irradiation temperature with 1 MeV Kr ions. The mixing parameter in the GaAs matrix was ≈140 A(ring)5/eV at temperatures between 110 and 473 K, but dropped to ≈120 A(ring)5/eV at 573 K. The value was smaller in the AlAs matrix, ≈90 A(ring)5/eV between 110 and 473 K, but it increased to ≈120 A(ring)5/eV between 473 and 625 K. Ion beam mixing in a trilayer sample, GaAs/AlAs/GaAs, was also measured for comparison. At the deeper interface, AlAs on GaAs, and low temperature, the mixing parameter was 440 A(ring)5/eV, but only 250 A(ring)5/eV at the other interface, GaAs on AlAs. Mixing at the lower interface decreased at 573 K to 160 A(ring)5/eV while it decreased at 473 K at the other interface to 110 A(ring)5/eV. These results are interpreted on the basis of the influence of crystal structure on ion beam mixing.
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