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  • 1
    Electronic Resource
    Electronic Resource
    Influence of domain size on optical properties of ordered GaInP2 (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2633-2639 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using dark-field transmission electron microscopy images of ordered GaInP samples, we show how the ordering domain size depends on the growth temperature. Samples with different average domain sizes are compared with regard to their photoluminescence (PL) and excitation spectra. We find a close correlation between the size of the ordered domains and the relative intensity of the PL peak from band–band recombination compared with the rapidly shifting, below-band-gap luminescence emission. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361099
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  • 2
    Electronic Resource
    Electronic Resource
    Optical transitions and carrier relaxation in self assembled InAs/GaAs quantum dots (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4019-4026 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental results concerning optical transitions and carrier dynamics (capture and relaxation) in self assembled InAs/GaAs quantum dot structures grown by metalorganic vapor phase epitaxy. Photoluminescence (PL) measurements at high excitation level reveal optical transitions above the ground state emission. These transitions are found to originate from occupied hole states by solving the quantum dot eigenvalue problem. Time-resolved studies after non-resonant pulse excitation exhibit a relaxation ladder of the excited carriers from the GaAs barrier down to the ground state of the quantum dots. From both the continuous-wave measurements and the PL-decay curves we conclude that the carrier relaxation at non-resonant excitation is mediated by Coulomb interaction (Auger effect). PL-decay curves after resonant pulse excitation reveal a longer rise time compared to non-resonant excitation which is a clear indication of a relaxation bottleneck inside the quantum dots. We interpret the rise time (≈ 400 ps) in this case to originate from relaxation via scattering by acoustic phonons. The PL-decay time of the ground state emission ≈700 ps is interpreted as the excitonic lifetime of the quantum dot. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363361
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  • 3
    Electronic Resource
    Electronic Resource
    Role of electron traps in the excitation and de-excitation mechanism of Yb3+ in InP (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1523-1530 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental study concerning the excitation mechanism of the Yb impurity in n- and p-type InP crystals was performed by the method of optically detected microwave-induced impact ionization. Based on the results it is argued that the Yb3+ core excitation is intermediated by a nonradiative recombination of a bound exciton. A fingerprint of the existence of such an excitonic state is given. Also, the nonradiative decay channel is discussed and shown to involve an Auger process with the energy transfer to a locally bound electron. Experimental evidence is presented that by the impact ionization of the bound electron the nonradiative recombination channel may be removed, leading to an increase of the characteristic Yb3+ luminescence. An unprecedented microwave-induced 5% increase of the Yb3+ intrashell emission has been recorded. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358903
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  • 4
    Electronic Resource
    Electronic Resource
    Intra- and interwell transitions in GaInN/GaN multiple quantum wells with built-in piezoelectric fields (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 82-84 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied optical transitions in GaInN/GaN single and multiple quantum wells using time-resolved photoluminescence spectroscopy. Our results show that the energy positions of the dominant emission lines strongly depend both on the well width and on the number of wells. In the case of multiple quantum wells, time-resolved measurements clearly distinguish multiple emission lines. These observations are consistently explained by considering the large built-in piezoelectric field in strained GaInN quantum wells. The multiple emission lines are attributed to intra- and interwell transitions between nearest and next-nearest neighbors. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122958
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  • 5
    Electronic Resource
    Electronic Resource
    Hole transport over heterobarriers in InP based multiple quantum well structures (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1323-1325 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a systematic analysis of the hole transport over heterobarriers in the InGaAs(P)/InP material system. The experiments have been performed on our recently developed all-optical switching structures [C. Knorr et al., Appl. Phys. Lett. 69, 4212 (1996)], which offer an elegant access to hole transport rates. We have varied barrier thickness, barrier height, bias voltage, and temperature. The time constants vary from 30 μs to 30 ns. Our model calculations, including all heavy and light hole subbands, show that only thermally assisted tunneling can explain both the temperature and electric field dependence of the transport rates. We have extracted the activation energies. The hole capture time is determined as 250±50 fs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120982
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  • 6
    Electronic Resource
    Electronic Resource
    Single variant ordering in GaInAs/InP (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2127-2129 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spontaneously ordered Ga0.47In0.53As grown on substrates with the (001) surface tilted 4° towards {111}B are studied using spectroscopic methods as well as x-ray diffraction, transmission electron diffraction and dark-field transmission electron microscopy. The single variant ordering is proved by the absence of one class of the ordering induced 〈fraction SHAPE="CASE"〉12{111}B superlattice spots in transmission electron diffraction patterns as well as by the tilted polarization of the photoluminescence emerging from the samples cleaved edge. The temperature dependence of the luminescence peak position shows an anomalous behavior at low temperatures and a strong dependence of the peak position on the excitation power. From low temperature absorption measurements, we find a band gap reduction of 37 meV and a valence band splitting of 13.2 meV. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119357
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  • 7
    Electronic Resource
    Electronic Resource
    A mechanism for low-power all-optical switching in multiple-quantum-well structures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 4212-4214 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a novel type of optical switching mechanism in pin separate confinement multiple quantum well (SCMQW) structures. By introducing additional large barriers into conventional InGaAs(P)/InP SCMQW structures, the transport of photogenerated holes can be controlled in such a way that they accumulate in the intrinsic region. This positive space charge leads to a local screening of the internal field in the optical confinement layer and to an enhancement of the internal field in the MQW region. We characterize the optical nonlinearity, which is based on the quantum confined Stark effect (QCSE), experimentally and theoretically. As the nonlinearity is observed at input powers 〈1 W/cm2 in the basic nonoptimized structures presented here, we propose to use our structure especially for low-power optical switches. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116989
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  • 8
    Electronic Resource
    Electronic Resource
    Deep-level defects and n-type-carrier concentration in nitrogen implanted GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2525-2527 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyzed the intrinsic defects and the n-type-carrier concentration generated by nitrogen ion implantation in n-type GaN by deep-level-transient spectroscopy and by capacitance–voltage measurements, respectively. The samples were grown on sapphire by metalorganic vapor-phase epitaxy. Nitrogen implantation with different ion doses and postimplantation rapid-thermal annealing (RTA) were investigated. We observed a growing n-type-carrier concentration and increasing defect concentration with increasing nitrogen ion implantation doses. After RTA the concentration of free carriers and deep levels as found in the as-grown state are restored. We also address contrarily seeming results from measurements of sheet resistance after N implantation published recently. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117727
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  • 9
    Electronic Resource
    Electronic Resource
    Optical gain in GaInN/GaN heterostructures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3746-3748 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By optical gain spectroscopy we have studied the fundamental laser properties of GaInN/GaN heterostructures grown on sapphire. Utilizing the stripe excitation method we have measured optical gain spectra at room temperature. Due to the low symmetry of the wurtzite structure and the resulting splitting of the uppermost valence bands, we find optical gain only for the TE mode. Our analysis shows that the optical gain is due to direct band-to-band transitions in an electron-hole plasma. For gain amplitudes typically found in lasers, we find carrier densities up to 3×1019 cm−3, which are likely to lead to rather large threshold current densities. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115993
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  • 10
    Electronic Resource
    Electronic Resource
    New near-infrared defect luminescence in GaN doped with vanadium by ion implantation (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 203-204 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a new photoluminescence (PL) spectrum of wurzite-type GaN intentionally doped with vanadium by ion implantation. A group of several broad intense near-infrared PL lines is observed at 820 meV. The whole PL spectrum can be observed up to room temperature. The samples were grown by low-pressure metalorganic vapor phase epitaxy on sapphire substrate. After ion implantation the samples were annealed under growth conditions at 920 °C. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116460
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