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  • 11
    Electronic Resource
    Electronic Resource
    Analysis of optical gain and threshold current density of wurtzite InGaN/GaN/AlGaN quantum well lasers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1813-1819 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The valence subband structures, density-of-states, and optical gain of (0001) wurtzite InxGa1−xN/GaN quantum wells (QWs) are studied using a numerical approach. We used the effective-mass parameters of GaN and InN derived using the empirical pseudopotential method. By varying the well width and mole fraction of In in the well material, the effects of quantum confinement and compressive strain are examined. A narrower well width and a higher In mole fraction in the well lead to transverse electric enhancement and transverse magnetic suppression of the optical gain. From the relationship between the optical gain and the radiative current density, we obtain the transparent current density for a single QW to be 200 A/cm2. The InGaN/GaN/AlGaN separate confinement heterostructure multiple QW (MQW) laser structure is then analyzed. It is shown that a suitable combination of well width and number of QWs should be selected in optimizing the threshold current density in such MQW lasers. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368338
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  • 12
    Electronic Resource
    Electronic Resource
    Electronic band structures and effective-mass parameters of wurtzite GaN and InN (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1429-1436 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic band structures of wurtzite GaN and InN are calculated by the empirical pseudopotential method (EPM) with the form factors adjusted to reproduce band features which agree with recent experimental data and accurate first-principles calculations. The electron and hole effective masses at the Γ point are obtained using a parabolic line fit. Further, using the effective-mass Hamiltonian and the cubic approximation for wurtzite semiconductors, band edge dispersion at the Γ point obtained using the k.p method is fitted to that calculated using the EPM by adjusting the effective-mass parameters. Thus, we derived important band structure parameters such as the Luttinger-like parameters for GaN and InN which will be useful for material design in wide-gap nitride-based semiconductor lasers employing InGaN. The results also showed that the cubic approximation is fairly successful in the analysis of valence band structures for wurtzite nitrides. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366847
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  • 13
    Electronic Resource
    Electronic Resource
    Noise reduction mechanisms in laminated antiferromagnetically coupled recording media (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2423-2425 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental methods to obtain remnant moment-thickness product (Mrδ) reduction in the laminated antiferromagnetically coupled (LAC) recording media is described. The results indicate that the reduction in Mrδ (or, indirectly, a reduction in noise) can be obtained by altering the antiferromagnetic coupling constant J, or by the parameters of the underlayer such as anisotropy constant (Ku2), thickness (t2), etc. A method to enhance J by intrinsic means is proposed by which a high exchange field of about 1900 Oe can be obtained. Thermal energy has been found to help in obtaining a Mrδ reduction in LAC media. Substrates with lower surface roughness also enhance the Mrδ reduction. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1407855
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  • 14
    Electronic Resource
    Electronic Resource
    Asymmetry diffraction magneto-optical phenomenon of NiFe grating (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2034-2036 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the asymmetry of longitudinal magneto-optical Kerr loops obtained from diffracted spots of a NiFe grating. The analysis of several series of diffracted Kerr hysteresis loops reveals that the unsaturated magnetic structure not only contributes to the shape change of Kerr loops, but also results in asymmetric feature of Kerr loops because of the nonzero value of second-order magnetic response. A suitable pattern dimension, which defines the form factor, is helpful to observe asymmetry Kerr loops. Our experiment indicates that out-of-incidence-plane diffraction may offer an alternative method to observe lateral edge domain movements in patterns. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1404126
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  • 15
    Electronic Resource
    Electronic Resource
    Trap signatures of As precipitates and As-antisite-related defects in GaAs epilayers grown by molecular beam epitaxy at low temperatures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2543-2545 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Despite many separate studies of the two dominant defects, i.e., As precipitates and arsenic-antisite (AsGa)-related traps, in GaAs epilayers grown by molecular beam epitaxy at low temperatures, they are seldom examined simultaneously. In this letter, we report the detection of both defects in electron trap spectrum obtained by zero quiescent bias voltage transient current spectroscopy. The As precipitates appear as a broad continuum of states in the lower temperature region (〈280 K) of the spectra whereas the AsGa-related defect appears as a discrete peak at a higher temperature. The AsGa-related trap has an activation energy of 0.65 eV and a capture cross section of 9.3×10−14 cm2. It is found that the trap characteristic of low temperature GaAs is strongly dependent on its growth temperature and the above mentioned defects may not dominate in some cases. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117733
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  • 16
    Electronic Resource
    Electronic Resource
    Dislocations and related traps in p-InGaAs/GaAs lattice-mismatched heterostructures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2849-2851 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dislocations and traps in p-InGaAs/GaAs lattice-mismatched heterostructures are investigated by cross-section transmission electron microscopy (XTEM) and deep level transient spectroscopy (DLTS). The misfit dislocations and threading dislocations observed by XTEM in different samples with different In mole fractions and different InGaAs layer thicknesses over all satisfy the Dodson–Tsao plastic flow critical layer thickness curve. By comparing the XTEM and DLTS results, we identify that the threading dislocations in bulk layers introduce three hole trap levels H1, H2, and H5 with DLTS activation energies of 0.32, 0.40, and 0.88 eV, respectively, and one electron trap level E1 with a DLTS activation energy of 0.54 eV. The misfit dislocations in the relaxed InGaAs/GaAs interface induce a hole trap level H4 with a DLTS activation energy of 0.67–0.73 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117339
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  • 17
    Electronic Resource
    Electronic Resource
    Properties of ion exchanged planar and channel optical waveguides fabricated in Cu doped KTiOPO4 substrates (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2737-2739 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Planar and channel optical waveguides were fabricated in Cu doped KTiOPO4 (KTP) substrates using Rb+:K+ ion exchange process and annealing process. The effective refractive indices were measured using the m-line method and the refractive index profiles of these waveguides were calculated using the inverse WKB method. For waveguides in Cu:KTP substrates the difference of diffusion depth d and index change Δn at the z− and z+ surfaces can hardly be observed. This observation is different from KTP. Compared with undoped KTP substrates the diffusion depth d at the z− surfaces is larger, whereas the index change Δn is smaller. At the z+ surfaces both d and Δn are larger. The light induced effective index changes in Cu doped KTP channel waveguides were measured at 0.476, 0.488, 0.514, 0.6328, and 0.83 μm wavelengths. No changes were observed at the power flow of 1×108 W/m2, revealing that Cu ion does not play an important role in photorefractive effect of KTP crystals. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120122
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  • 18
    Electronic Resource
    Electronic Resource
    High oxygen and carbon contents in GaAs epilayers grown below a critical substrate temperature by molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 841-843 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By quantitative secondary ion mass spectroscopy (SIMS) analyses, oxygen and carbon contents in GaAs epitaxial layers grown by molecular beam epitaxy (MBE) were found to increase significantly when the growth temperature was reduced below a critical value at about 450 °C. The concentrations of oxygen and carbon in GaAs epilayers grown below the critical temperature were about 4×1017 cm−3 and 3×1016 cm−3, respectively. Meanwhile, impurity accumulation during growth interruption became faster resulting in even higher interfacial impurity concentrations. Oxygen and carbon will affect the electrical properties of the GaAs epilayers, especially those grown between 350 °C and 450 °C where defects related to excess As may not be dominating. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116551
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  • 19
    Electronic Resource
    Electronic Resource
    Nanoscale cube-on-cube growth of SrS on MgO substrate by solid-source molecular-beam epitaxy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 115-117 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth of epitaxial SrS on (001)MgO substrates by solid-source molecular-beam epitaxy. During the deposition, the film structure and orientation were characterized by reflection high-energy electron diffraction. It was shown that the film epitaxial planes conserved the substrate surface symmetry—cubic. X-ray diffraction results establish the epitaxial relationship as cube-on-cube (001)SrS ||(001)MgO with [100]SrS ||[100]MgO for growth temperature between 400 and 600 °C. Scanning electron microscopy and atomic force microscopy analyses were used to study the films' surface morphology. Depending on the growth temperature, different sizes of SrS islands can be achieved. The growth of SrS on MgO is thought to occur in step-flow growth mode. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429759
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  • 20
    Electronic Resource
    Electronic Resource
    Thermal energy consideration in micromagnetic simulation for laminated antiferromagnetically coupled recording media (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1646-1648 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Contribution of thermal energy, has been included in the micromagnetic simulation of laminated antiferromagnetically coupled (LAC) media. The antiferromagnetic coupling constant, J, required to obtain Mrt reduction in the existing simulation studies (T=0 K) of LAC media is much higher than the experimental values. In this letter, we describe some experimental results, which point out that the contribution of thermal energy in Mrt reduction is significant. Consequently, we find that the values of J and the reversal fields are comparable to the experimental results, when thermal energy (T=300 K) is included in the simulation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402658
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