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  • 1
    Electronic Resource
    Electronic Resource
    Photorefractive InGaAs/GaAs multiple quantum wells in the Franz–Keldysh geometry (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5889-5896 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We fabricate semi-insulating InGaAs/GaAs multiple quantum wells and observe the excitonic enhancement of the photorefractivity in the Franz–Keldysh geometry at wavelengths of 0.92–0.94 μm. A maximum two-wave mixing gain of 138 cm−1 and a maximum diffraction efficiency of 1.5×10−4 are obtained. The saturation intensity and the spatial resolution are also measured by four-wave mixing. The diffraction efficiency is saturated at a high external electric field. The dominant cause of this saturation is the deviation of the excitonic electroabsorption from its quadratic law. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370364
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  • 2
    Electronic Resource
    Electronic Resource
    Detection of oxygen incorporated in molecular-beam epitaxy grown GaAs-on-AlAs interfaces and AlAs layers by secondary ion mass spectrometry (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1924-1926 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By employing a long growth interruption (GI) in molecular beam epitaxy, we have successfully determined the concentration of oxygen incorporated in GaAs/AlAs interfaces and AlAs layers by secondary ion mass spectrometry. The concentration of oxygen atoms incorporated on AlAs surfaces during GI is found to be proportional to the period of GI when the incoming fluxes of residual oxygen-related species reach steady-state values. The net incorporation rate of oxygen on the AlAs surface is found to be constant for a wide range of substrate temperatures from 540 to 620 °C, indicating that the oxygen desorption is negligible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110650
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  • 3
    Electronic Resource
    Electronic Resource
    Tightly confined one-dimensional states in T-shaped GaAs edge quantum wires with AlAs barriers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3672-3673 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have designed and prepared a T-shaped GaAs edge quantum wire (T-QWR) structure with AlAs barriers by cleaved edge overgrowth method. Three photoluminescence (PL) peaks have been observed and their origins are identified using the spatially resolved PL technique. The effective binding energy of carriers in this T-QWR is precisely determined as the energy spacing between T-QWRs and the adjacent QWs. When the well width of constituent QWs was 5 nm, the effective binding energy is found to be as large as 35 meV, which is far beyond the thermal energy kT at room temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114136
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  • 4
    Electronic Resource
    Electronic Resource
    Transport properties of two-dimensional electron gas in AlGaAs/GaAs selectively doped heterojunctions with embedded InAs quantum dots (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3444-3446 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transport properties of two-dimensional electron gas (2DEG) are studied in selectively doped GaAs/n-AlGaAs heterojunctions, in which nanometer-scale InAs dots are embedded in the vicinity of the GaAs channel. When the distance Wd between the InAs dot layer and the channel is reduced from 80 to 15 nm, the mobility μ of electrons at 77 K decreases drastically from 1.1×105 to 1.1 ×103 cm2/V s, while the carrier concentration increases from 1.1×1011 to 5.3×1011 cm−2. Such a reduction of mobility is found only when the average thickness of InAs layer is above the onset level (∼1.5 monolayer) for the dot formation. Origins of these changes in μ and Ns are discussed in connection with dot-induced modulations of the electronic potential V(r) in the channel. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115274
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  • 5
    Electronic Resource
    Electronic Resource
    Nanometer-scale InGaN self-assembled quantum dots grown by metalorganic chemical vapor deposition (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 383-385 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have successfully grown nanometer-scale InGaN self-assembled quantum dots (QDs) on a GaN surface without any surfactants, using atmospheric-pressure metalorganic chemical vapor deposition. Atomic force microscopy shows that the average diameter of InGaN QDs is as small as 8.4 nm. Next, we have investigated the dependence of the QDs properties on the growth conditions: the amount of InGaN deposited and the growth temperature. Moreover, we have investigated the optical property of InGaN QDs, so that the strong emission was seen at 2.86 eV at room temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123078
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  • 6
    Electronic Resource
    Electronic Resource
    Highly reflective GaN/Al0.34Ga0.66N quarter-wave reflectors grown by metal organic chemical vapor deposition (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3653-3655 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quarter-wave reflectors consisting of sets of GaN and Al0.34Ga0.66N layers have been grown on sapphire substrates by atmospheric-pressure metal organic chemical vapor deposition. A periodic structure with flat interfaces was observed by high-resolution scanning electron microscopy. X-ray diffraction measurements were performed to characterize the structures, from which the Al content x in the AlxGa1−xN layers was determined to be 0.34. No cracks could be seen on the surface of the reflectors by optical microscopy. The measured peak reflectivity at 390 nm increases with the number of pairs and reaches as high as 96±2% in the 35-pair reflector. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122852
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  • 7
    Electronic Resource
    Electronic Resource
    Time-resolved photoluminescence of GaN/Al0.5Ga0.5N quantum wells (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1005-1007 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report photoluminescence (PL) and time-resolved PL measurements of GaN/AlxGa1−xN multiple quantum wells with barriers of high aluminum content, x=0.5. In wells of width 1–2 nm, low temperature recombination appears to be dominated by radiative processes with lifetimes ∼0.5 ns. Dependence of lifetime on emission energy is very small compared to InGaN quantum wells, indicating that carrier localization is very slight and interface quality is high. In 4 nm wells, PL emission at an energy below the bulk GaN band gap and long recombination lifetimes result from the polarization field across the wells. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289041
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of carrier confinement on photoluminescence from modulation-doped AlxGa1−xN/GaN heterostructures (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 679-681 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) of modulation-doped Al0.22Ga0.78N/GaN heterostructures was investigated. The PL peak related to recombination between the two-dimensional electron gases (2DEG) and photoexcited holes is located at 3.448 eV at 40 K, which is 45 meV below the free excitons (FE) emission in GaN. The peak can be observed at temperatures as high as 80 K. The intensity of the 2DEG PL peak is enhanced significantly by incorporating a thin Al0.12Ga0.88N layer into the GaN layer near the heterointerface to suppress the diffusion of photoexcited holes. The energy separation of the 2DEG peak and the GaN FE emission decreases with increasing temperature. Meanwhile, the 2DEG peak energy increases with increasing excitation intensity. These results are attributed to the screening effect of electrons on the bending of the conduction band at the heterointerface, which becomes stronger when temperature or excitation intensity is increased. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125859
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of strain relaxation of the AlxGa1−xN barrier on transport properties of the two-dimensional electron gas in modulation-doped AlxGa1−xN/GaN heterostructures (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2746-2748 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Influences of the thickness of the Si-doped n-type Al0.22Ga0.78N barrier and the thickness of the Al0.22Ga0.78N spacer on mobility and density of the two dimensional electron gas (2DEG) in modulation-doped Al0.22Ga0.78N/GaN heterostructures were investigated. 2DEG mobilities of 1274 cm2/V s at 300 K and 4495 cm2/V s at 77 K were reached. Both 2DEG mobility and density decrease dramatically when the Al0.22Ga0.78N barrier becomes partially relaxed, indicating that transport properties of the 2DEG are influenced significantly by the piezoelectric polarization of the Al0.22Ga0.78N layer. From our results, the critical thickness of an Al0.22Ga0.78N layer on GaN is estimated to be between 65 and 75 nm, which is much higher than that predicted by theoretical calculation. This may be attributed to the interaction of misfit dislocations and the presence of a high density of extended defects in the Al0.22Ga0.78N layer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126463
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  • 10
    Electronic Resource
    Electronic Resource
    Observation of enhanced spontaneous emission coupling factor in nitride-based vertical-cavity surface-emitting laser (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 722-724 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate an enhancement of spontaneous emission coupling factor β in a nitride-based vertical-microcavity surface-emitting laser. The 2.5λ vertical microcavity, the quality factor of which reaches 740, is sandwiched between a nitride and an oxide distributed Bragg reflector. From input–output measurements and analyses of the rate equations, the β of the lasing mode at a wavelength of 396.1 nm is estimated to be 1.6×10−2. The estimated β can be well accounted for by a simple theoretical model. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430855
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