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  • 1
    Electronic Resource
    Electronic Resource
    Alloy composition dependence of defect energy levels in GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S (x≤0.24) (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1862-1867 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defect energy levels in metalorganic chemical vapor deposition (MOCVD) grown GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S epilayers (x≤0.24) have been studied by photoluminescence (PL) and photoconductivity (PC) measurements. To understand the origin of the observed deep levels, we have determined the temperature dependence of the intensity and half-width of the dominant deep-level PL peaks. We find that (1) the dominant deep-level peaks of the samples grown on the same substrate are related to the epilayer composition, and move to higher energies with increasing gallium content; (2) the dominant deep-level peaks of the samples with the same epilayer composition grown on different substrates are different. They are attributed to the impurity in the substrate diffusing into the epilayer during MOCVD growth, forming an impurity-vacancy complex. The following tentative assignments are proposed: the dominant deep-level peaks in GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S are attributed to the emission of a (V)P-(Fe)III complex and a (V)III-(S)P complex, respectively. Comparing the deep level with the near-band-edge emission we show that (1) all deep levels are independent of the band edge as x is varied; (2) the composition dependences of the deep levels associated with such complexes depend on the site occupied by the impurity atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354794
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature dependence of photoluminescence in InAsP/InP strained multiple quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5921-5926 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoluminescence spectra of InAsP/InP strained multiple quantum wells have been experimentally determined in the temperature range 7–300 K. In order to understand the temperature behavior of the photoluminescence, a theoretical calculation is presented that takes into account the temperature-induced variations in band gap, carrier effective mass, biaxial strain, and exciton binding energy. The results show that the energy of the transition E1H between the n=1 electron subband and the n=1 heavy-hole subband changes as a function of temperature, and depends mainly on the evolution of the strained band gap of the InAsP layers. This is because in the temperature range 7–300 K the variations of the electron subband energy and the exciton binding energy are much less than those of the strained band gap, while the variation of the heavy-hole subband energy can be neglected. These results also explain why, for a lattice-matched quantum well, the variation of exciton peak energies with temperature follows that of the forbidden energy gap of the bulk material in the well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358481
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of interface roughness and well width on differential reflection dynamics in InGaAs/InP quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 97-99 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed differential reflection dynamics in In0.518Ga0.492As/InP multiple quantum wells, using the pump–probe technique, and examined the photoluminescence spectra to determine the interface quality for the samples studied. Our results show that the interface quality and well width of the quantum wells (QWs) strongly influence the differential reflection dynamics. The experimental results provide a direct evidence to demonstrate that photoexcited carrier diffusion in cap layer and barriers along the direction perpendicular to sample surface plays a dominant role in determining the differential reflection dynamics of the QWs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120656
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  • 4
    Electronic Resource
    Electronic Resource
    Differential reflection dynamics in InAsxP1−x/InP (x≤0.35) strained-multiple-quantum wells (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4430-4435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using the pump-probe technique, we have observed time-resolved differential reflection in InAsxP1−x/InP (x≤0.35) strained-multiple-quantum wells. The experimental results show that barrier height, interface roughness and well width influence strongly the differential reflection dynamics. For samples with the same interface quality and almost the same well width, the delay time of the differential reflection decreases with increasing barrier height, while for the sample with rough interface and narrower wells, the delay time of the differential reflection is much slower, although it has a larger barrier height. To understand the experimental results, we have performed a simulation study of temporal and spatial evolutions of photoexcited carriers in the samples, and the influence of various physics processes on the photoexcited carrier dynamics has been discussed. From the calculated and the measured results, we conclude that carrier diffusion in the cap layer and the barriers plays a dominant role in determining the differential reflection dynamics. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367202
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  • 5
    Electronic Resource
    Electronic Resource
    Laser power and temperature dependence of the transient photoimpedance response of epitaxial YBa2Cu3O7−δ thin films (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1531-1535 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of laser power on the transient response of photoimpedance and the in situ sample temperature is studied for epitaxial YBa2Cu3O7−δ (YBCO) films at a wavelength of 810 nm using 100 fs laser pulses. The temperature dependences of the dc resistance and the amplitudes of the fast and slow photoresponse signals were measured simultaneously. For laser energy density of 20 μJ/cm2 per pulse (average power 22 mW), the average sample temperature is found to increase by about 1 K for 300 nm thick YBCO film with 0.5 mm thick LaAlO3 substrate as shown by the shift of resistance versus temperature curves. Calculations of time constant show that heat diffusion in LaAlO3 is the bottleneck for heat escape which causes the observed increase of the sample temperature. The amplitudes of both slow and fast signals show a peak in the temperature dependence curves near the superconducting transition temperature; and the peak temperature decreases, while the peak amplitude increases with laser power. At 82 K, the laser power dependence of the fast signal amplitude showed nonlinear behavior above 22 mW. These data were analyzed in terms of the kinetic inductance model and bolometric mechanism for the fast and slow signals, respectively. The temperature variation owing to laser pulse has been taken into consideration in this analysis. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366862
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of oxygen content on the structural, transport, and magnetic properties of La1−δMn1−δO3 thin films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6327-6330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: (110) oriented La1−δMn1−δO3 thin films with different oxygen content were grown on (001) LaAlO3 substrates by pulsed laser deposition. Samples prepared in higher oxygen partial pressures show a ferromagnetic transition around 200 K. The transport is thermally activated with a change in slope at the ferromagnetic transition. Samples prepared and annealed in vacuum show signatures of mixed ferromagnetic and antiferromagnetic phases, and are insulators. The pure antiferromagnetic phase (as expected and observed in bulk materials with optimum oxygen stoichiometry) was not obtained in our experiments, even in the strongly reduced films. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371693
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  • 7
    Electronic Resource
    Electronic Resource
    Growth of single-phase PrBa0.7Sr1.3Cu3O7 thin films and the role of lattice strain on the transport properties (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 981-983 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-phase PrBa0.7Sr1.3Cu3O7 thin films with the Sr dopant concentration exceeding the solid solubility limit were epitaxially grown on (001) SrTiO3 and (001) LaAlO3 substrates by pulsed laser deposition (PLD) method. The resistivity of the doped films grown on LaAlO3 was significantly lower than that of PrBa2Cu3O7. For most of the films grown on SrTiO3, the resistivity was higher than that of PrBa2Cu3O7. The results were explained by considering the Sr-doping effect and lattice-mismatch-induced strain effect. This work shows the potential of PLD to grow single-phase films with the dopant concentration exceeding the solid solubility limit. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120615
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  • 8
    Electronic Resource
    Electronic Resource
    Far-field and beam characteristics of vertical-cavity surface-emitting lasers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1829-1831 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have determined the far-field patterns and beam parameters of vertical-cavity surface-emitting lasers (VCSELs) with different structures. The results show that the window diameter and the active-layer aperture of VCSELs strongly influence laser far-field distributions and beam characteristics; for VCSELs with small window ω=5 μm, only one dominant lobe has been observed in the far-field profiles, even though injected current was increased up to 2 Ith; and the smaller the ratio of the window diameter to the active-layer aperture, the larger is the far-field divergence. The laser structure dependence of the K factor has also been studied. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117447
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  • 9
    Electronic Resource
    Electronic Resource
    Ultraviolet lasing in resonators formed by scattering in semiconductor polycrystalline films (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3656-3658 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A semiconductor laser whose cavities are "self-formed" due to strong optical scattering in highly disordered gain media is demonstrated. The lasers are made of zinc oxide polycrystalline films grown on amorphous fused silica substrates. Lasing occurs at an ultraviolet wavelength of ∼380 nm under optical pumping. Actual images of the microscopic laser cavities formed by multiple scattering have been captured. These results suggest the possibility of using disordered semiconductor microstructures as alternative sources of coherent light emission. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122853
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  • 10
    Electronic Resource
    Electronic Resource
    Alloy composition dependence of photoexcited carrier dynamics in GaxIn1−xP/InP:Fe (x〈0.18) (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 696-698 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed the reflection recovery dynamics of photoexcited GaxIn1−xP/InP:Fe (x〈0.18), using the pump-probe technique, and found that the delay time of the reflection recovery dynamics increases with increasing gallium composition. To understand the experimental results, we have also performed a simulation study, which is in good agreement with the measured data, and shows that ambipolar diffusion plays a dominant role in determining the photoexcited carrier dynamics. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116595
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