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  • 1990-1994  (17)
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Erscheinungszeitraum
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  • 1
    Digitale Medien
    Digitale Medien
    Photoreflectance studies of lattice-matched and strained InGaAs/InAlAs single quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1437-1439 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Lattice-matched and strained InxGa1−xAs/In0.52Al0.48As single quantum wells with x=0.53 and x=0.60 have been studied by the optical modulation technique of photoreflectance (PR) at room temperature. The measurements have allowed the observation of interband transitions from the heavy- and light-hole valence subbands to the conduction subbands. The PR data have been adjusted with a least-squares fit to the first-derivative functional form. The energetic positions of the optical transitions deduced from the fit have been compared with theoretical values obtained by an envelope function model calculation including strain effects. The best adjustment allowed the determination of the conduction-band offset parameter Qc which is found equal to 0.71±0.07 for the lattice-matched and strained compositions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354904
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  • 2
    Digitale Medien
    Digitale Medien
    Passivation induced deep levels in GaInAs PIN planar photodiodes (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4436-4439 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The damage induced by the passivation process has been evaluated and compared by admittance and deep level transient spectroscopies in GaInAs planar photodiodes passivated by a silicon nitride film. The comparison is based on three deposition techniques: the chemical vapor deposition (CVD), the plasma-enhanced CVD (PECVD), and the ultraviolet activated CVD (UVCVD). Two deep levels, with properties and concentration which are found to be strongly dependent on the passivation techniques, are observed: The first, located at Ec−0.35 eV is detected in PECVD and UVCVD passivated diodes and attributed to the GaInAs surface degradation resulting from the deposition process. The second, located at Ec−0.19 eV appears only on CVD diodes and could be related to the high-temperature treatment specific to this technique.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.350784
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  • 3
    Digitale Medien
    Digitale Medien
    Electrical characterization of a GaAs quantum well confined by GaAlAs layers or by two superlattices (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4134-4138 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Capacitance-voltage, deep level transient spectroscopy (DLTS), and admittance spectroscopy measurements have been performed to characterize a GaAs quantum well confined either by Ga0.57Al0.43As layers or by two GaAs-Ga0.54Al0.46As superlattices. Due to a large capacitance decrease at low temperature, the well response cannot be obtained from DLTS measurements. This capacitance step is related to the thermionic emission from the well to the barrier regions. For the case of the enlarged well in the superlattice, the electron emission takes place towards the conduction miniband. In order to deduce the conduction-band discontinuity, admittance spectroscopy measurements have been applied. The bottom of the superlattice miniband is at 107±10 meV from the GaAs conduction-band minimum. The corresponding band offset deduced from a theoretical calculation is ΔEc=410±10 meV=(0.65±0.02) ΔEg. For the GaAs quantum well in GaAlAs, we measure a conduction-band discontinuity of 0.35 eV between GaAs and GaAlAs that has its minimum at the X point. At the Γ point, the band offset ratio ΔEc/ΔEg is once more confirmed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352221
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  • 4
    Digitale Medien
    Digitale Medien
    Stoichiometry-dependent native acceptor and donor levels in Ga-rich-n-type gallium arsenide (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3325-3329 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: By combining photoluminescence and optical deep-level transient spectroscopy measurements, we have investigated the presence of a native acceptor level H01 situated at 0.32 eV above the valence band, in n-type Si-doped liquid-encapsulated Czochralski GaAs grown in stoichiometric and Ga-rich conditions. The concentration of H01 decreases when increasing the [Ga]/[As] ratio up to a critical threshold of 1.3. For [Ga]/[As] ratio greater than 1.3, H01 disappears and another acceptor level, H02 (Ev+0.23 eV), is detected. H02 is identified as the double-acceptor level of the gallium antisite GaAs. Photoluminescence results show the presence of a high-intensity 1-eV band which disappears for [Ga]/[As] ratios greater than 1.2. The annihilation of this band is accompanied by the appearance of two emission bands centered at 0.95 and 1.2 eV. The dependence of the free-carrier concentration on the presence of H01 is interpreted in terms of a complex defect formed by a gallium vacancy and silicon impurity which can be the possible origin of this defect. Finally, the evolution of native electron traps present in these samples, with [Ga]/[As] ratio, is also interpreted to give more information about the origin of the EL6 center in GaAs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.350953
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  • 5
    Digitale Medien
    Digitale Medien
    Optical investigation in ultrathin InAs/InP quantum wells grown by hydride vapor-phase epitaxy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1638-1641 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Single and multiple InAs/InP strained quantum wells have been grown by hydride vapor-phase epitaxy (HVPE). A compact set of vent/run valves monitored by manifold switches and a computer allowed the vapor species to be changed. InAs growth times of 4–24 s followed by etching times of 7–14 s, in an InCl, HCl, and H2 atmosphere, were used to control the thickness and interface abruptness. Low-temperature photoluminescence (PL) spectra have revealed emissions either in the form of a single peak or well-resolved multiple peaks attributed to monolayer variation in quantum-well thickness. The thinnest well obtained, observed for the first time by HVPE, has a PL energy transition at 1.28 eV. Experimental data agree well with theoretical calculations, taking into account strain effects on band structure and effective masses. The full widths at half maximum indicate good interfacial abruptness.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349529
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  • 6
    Digitale Medien
    Digitale Medien
    Iron-catalyzed oxidation of bis(imidazol-2-yl)methane into bis(imidazol-2-yl) ketone (1990)
    s.l. : American Chemical Society
    Inorganic chemistry 29 (1990), S. 577-579 
    Details
    ISSN: 1520-510X
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ic00329a001
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  • 7
    Digitale Medien
    Digitale Medien
    Determination of ionization energies of the nitrogen donors in 6H-SiC by admittance spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1956-1958 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The nitrogen donor levels have been studied by admittance spectroscopy between 20 and 200 K in Schottky barriers made on lightly n-type epitaxial 6H-SiC layers. Measurements at different frequencies yield different freezeout temperatures which in turn are used to determine the donor level energies. Two electron traps at Ec−0.082 eV and at Ec−0.140 eV were detected. These levels are associated with nitrogen, respectively, at the hexagonal sites for the former and at the cubic sites for the latter level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357655
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  • 8
    Digitale Medien
    Digitale Medien
    Optical and electrical properties of rare earth (Yb,Er) doped GaAs grown by molecular beam epitaxy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4171-4175 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electrical and optical properties of erbium-doped and ytterbium-doped GaAs are reported in this article. The studied samples are semi-insulating and have been grown by molecular beam epitaxy. The Yb and Er concentrations in the GaAs epitaxial layers measured by secondary ion mass spectroscopy are 2–3×1017 cm−3. The photoluminescence of Yb intra-4f shell has not been observed, while that of Er has been widely reported. Photoinduced current transient spectroscopy measurements (PICTS) reveal that the Yb doping (Er doping) creates a level in the gap with an activation energy of 0.65 eV (0.67 eV). The depth of such levels may be responsible for the absence of Yb 4f photoluminescence in GaAs:Yb. Moreover, photoconductivity experiments show the presence of rare earth related traps. The energies of these traps correspond exactly to the difference between the gap energy and the corresponding activation energy found by PICTS. These observations confirm the excitation model based on the energy transfer from recombination to the rare earth transitions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.356000
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  • 9
    Digitale Medien
    Digitale Medien
    Observation of photoluminescence from InAs surface quantum wells grown on InP(100) by molecular beam epitaxy (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1863-1865 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoluminescence (PL) measurements are presented for thin epitaxial layers of InAs, 2.5 A(ring)〈d 〈36 A(ring), grown on InP(100) by molecular beam epitaxy. The combination of efficient carrier capture and PL redshift with increasing InAs thickness clearly indicate the formation of InAs quantum wells on the InP surface. Data are also presented for InAs/InP structures capped with strained layers of either GaAs or In0.5 Al0.5 As. Since radiative recombination within the InAs layers can be distinguished from PL arising from both bulk and surface defects, this system allows us to monitor the quality of both the InAs/InP and InAs/air interfaces via their influence on the InAs quantum well luminescence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105055
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  • 10
    Digitale Medien
    Digitale Medien
    Characterization of DX centers in selectively doped GaAs-AlAs superlattices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1321-1323 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using deep level transient spectroscopy (DLTS), DX center has been characterized in GaAs-AlAs superlattices grown by molecular beam epitaxy and selectively Si-doped either in the AlAs layers or in the middle of the GaAs layers. The activation energy for thermal emission, which is the summation of the binding energy Et and the thermal capture energy Ec, is Ea=0.42 eV in both superlattices. The lowest DX concentration is obtained for the case where the only GaAs layers are doped. For the first time, a study of the capture reveals a capture activation energy Ec=0.36 eV, which locates the DX at Et≈60 meV below the conduction miniband. Taking into account the measured energies and trap concentrations, we show that the only observed DX on such structures is due to the silicon diffusion into AlAs layers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.103471
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