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  • 1
    Electronic Resource
    Electronic Resource
    Optical properties of GaN epilayers and GaN/AlGaN quantum wells grown by molecular beam epitaxy on GaN(0001) single crystal substrate (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 183-187 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN epilayers and GaN/AlGaN quantum wells (QWs) were grown by molecular beam epitaxy on GaN(0001) single crystal substrates. Transmission electron microscopy (TEM) was used to assess the crystal quality of the homoepitaxial layers. A dislocation density of less than 105 cm−2 is deduced from TEM imaging. Low temperature (1.8 K) photoluminescence (PL) of homoepitaxial GaN reveals PL linewidths as low as 0.3 meV for bound excitons. The PL integrated intensity variation between 10 and 300 K is compared to that observed on a typical heteroepitaxial GaN/Al2O3 layer. A 2 nm thick GaN/Al0.1Ga0.9N QW has been studied by time-resolved and continuous wave PL. The decay time is close to a purely radiative decay, as expected for a low defect density. Finally, the built-in polarization field measured in a homoepitaxial QW is shown to be comparable to that measured on heteroepitaxial QWs grown either on sapphire or silicon substrates. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373640
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  • 2
    Electronic Resource
    Electronic Resource
    Built-in electric-field effects in wurtzite AlGaN/GaN quantum wells (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3714-3720 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlGaN/GaN quantum well (QW) structures are grown on c-plane sapphire substrates by molecular beam epitaxy. Control at the monolayer scale of the well thickness is achieved and sharp QW interfaces are demonstrated by the low photoluminescence linewidth. The QW transition energy as a function of the well width evidences a quantum-confined Stark effect due to the presence of a strong built-in electric field. Its origin is discussed in terms of piezoelectricity and spontaneous polarization. Its magnitude versus the Al mole fraction is determined. The role of the sample structure geometry on the electric field is exemplified by changing the thickness of the AlGaN barriers in multiple-QW structures. Straightforward electrostatic arguments well account for the overall trends of the electric-field variations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371241
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  • 3
    Electronic Resource
    Electronic Resource
    Real time control of InxGa1−xN molecular beam epitaxy growth (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1078-1080 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of GaN and InxGa1−xN on c-plane sapphire substrates was carried out by molecular beam epitaxy using NH3. In situ reflection high-energy electron diffraction (RHEED) was used to monitor the growth process. Oscillations of the specular beam intensity were observed during both GaN and InxGa1−xN deposition. This allows determining in real time the composition of InxGa1−xN alloys. The effects of the growth temperature and the Ga flux on the In incorporation rate were investigated. The critical thickness for InGaN islanding as a function of In mole fraction is also easily deduced from RHEED experiments. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120970
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  • 4
    Electronic Resource
    Electronic Resource
    Ultraviolet GaN light-emitting diodes grown by molecular beam epitaxy using NH3 (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 82-84 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si- and Mg-doped GaN layers were grown on c-plane sapphire substrates by molecular beam epitaxy with NH3 as the nitrogen precursor. Their optical and electrical properties were investigated by photoluminescence experiments and Hall measurements, respectively. P-type conductivity, with a net acceptor concentration of 3×1017 cm−3 and a mobility of 8 cm2/V s, was obtained. Mesa-etched light-emitting diodes were processed from p–n junctions. The turn-on voltage is 3 V and the forward current reaches 20 mA at 3.5 V. The room-temperature electroluminescence exhibits a strong emission at 390 nm. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120651
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  • 5
    Electronic Resource
    Electronic Resource
    Gas source molecular beam epitaxy of wurtzite GaN on sapphire substrates using GaN buffer layers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 240-242 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wurtzite GaN was grown by gas source molecular beam epitaxy on (0001) sapphire substrates. Taking advantage of the catalytic decomposition of ammonia on the growing surface, high growth rates (〉1 μm/h) were achieved for substrate temperatures ranging between 800 and 850 °C. Surface morphology, structural, and optical properties of thick (2–4 μm) GaN films were investigated versus the growth temperature of the GaN buffer layer. It is shown that this parameter has a drastic influence on the GaN properties. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119526
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  • 6
    Electronic Resource
    Electronic Resource
    Nitridation of sapphire. Effect on the optical properties of GaN epitaxial overlayers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2071-2073 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN layers were grown by gas-source molecular beam epitaxy on sapphire substrates using ammonia as a nitrogen source. The nitridation of an Al2O3 surface prior to the GaN growth was followed in situ by reflection high-energy electron diffraction. A strong variation of the surface lattice parameter was observed corresponding to the formation of an AlN relaxed layer. The nucleation of GaN on such a nitridated surface is facilitated, as checked by atomic force microscopy. Optimization of the nitridation procedure is achieved by investigating the photoluminescence properties of GaN thin films grown for different nitridation times. It is found that the band-edge and the yellow-band luminescences are strongly dependent on the nitridated starting surface. Finally, the optimized nitridation process is used to grow high-quality GaN epitaxial layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116883
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular-beam epitaxy of gallium nitride on (0001) sapphire substrates using ammonia (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1379-1383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ammonia is used for growing undoped GaN layers by gas source molecular-beam epitaxy on c-plane sapphire substrates. The growth mode is layer by layer as shown by the observation of reflection high-energy electron diffraction intensity oscillations. The structural quality is studied by x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Low-temperature photoluminescence (PL) and reflectivity demonstrate intrinsic excitonic emission. Room-temperature PL exhibits a strong band-edge intensity and a weak deep-level emission, the so-called yellow band. Finally, secondary ion mass spectroscopy is carried out to check the residual impurity levels of Si, C, and O. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366840
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature quenching of photoluminescence intensities in undoped and doped GaN (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3721-3728 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work discusses the temperature behavior of the various photoluminescence (PL) transitions observed in undoped, n- and p-doped GaN in the 9–300 K range. Samples grown using different techniques have been assessed. When possible, simple rate equations are used to describe the quenching of the transitions observed, in order to get a better insight on the mechanism involved. In undoped GaN, the temperature dependence of band edge excitonic lines is well described by assuming that the A exciton population is the leading term in the 50–300 K range. The activation energy for free exciton luminescence quenching is of the order of the A rydberg, suggesting that free hole release leads to nonradiative recombination. In slightly p-doped samples, the luminescence is dominated by acceptor related transitions, whose intensity is shown to be governed by free hole release. For high Mg doping, the luminescence at room temperature is dominated by blue PL in the 2.8–2.9 eV range, whose quenching activation energy is in the 60–80 meV range. We also discuss the temperature dependence of PL transitions near 3.4 eV, related to extended structural defects. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371242
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  • 9
    Electronic Resource
    Electronic Resource
    Elastic misfit stress relaxation in highly strained InGaAs/GaAs structures (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1162-1164 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The strain contrasts associated with three-dimensional coherently strained islands formed during the epitaxial growth of highly strained In0.45Ga0.55As layers on GaAs (001) have been studied by transmission electron microscopy. It is demonstrated that the comparison of these experimental strain contrasts with simulated profiles makes it possible to assess the elastic relaxation of the islands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112128
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  • 10
    Electronic Resource
    Electronic Resource
    Surfactant mediated epitaxial growth of InxGa1−xAs on GaAs (001) (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 99-101 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that Te can be used as a surfactant for the growth of highly strained InxGa1−xAs on GaAs(001). As observed by reflection high-energy electron diffraction analysis during growth, adsorption of Te on the GaAs surface prior to the growth of InxGa1−xAs drastically increases the layer thickness which can be grown in a two-dimensional layer-by-layer fashion. In analogy with the behavior of As and Sb as surfactant in the growth of Si/Ge [Copel, Reuter, Kaxiras, and Tromp, Phys. Rev. Lett. 63, 632 (1989)] Te is only slightly incorporated in the growing layer and floats at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107626
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