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  • AIP Publishing  (22)
  • 1
    Online Resource
    Online Resource
    Terahertz dynamics of photogenerated carriers in ferromagnetic InGaMnAs
    AIP Publishing ; 2003
    In:  Journal of Applied Physics Vol. 93, No. 10 ( 2003-05-15), p. 8286-8288
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 93, No. 10 ( 2003-05-15), p. 8286-8288
    Abstract: We have measured the picosecond transient carrier response of InGaMnAs/InP by two-color pump–probe spectroscopy, using an intense near-infrared beam as the pump and a 52.5 μm (5.7 THz) beam as the probe. We observed strongly nonexponential decays, especially at high pump fluences and low temperatures, where a pronounced dip developed in the terahertz differential transmission. This dip disappeared at the highest fluence where a transmission plateau versus time delay was observed. Our band structure calculations suggest that this intriguing behavior may be due to carrier dynamics associated with Γ–L intervalley scattering that becomes efficient when ferromagnetism modifies the band structure.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1555375
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2003
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
    Online Resource
    Online Resource
    Probing strained InGaN/GaN nanostructures with ultrashort acoustic phonon wave packets generated by femtosecond lasers
    AIP Publishing ; 2002
    In:  Applied Physics Letters Vol. 80, No. 25 ( 2002-06-24), p. 4723-4725
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 80, No. 25 ( 2002-06-24), p. 4723-4725
    Abstract: Large amplitude time-domain oscillations are detected in InxGa1−xN/GaN structures via femtosecond differential reflectivity spectroscopy. The oscillation amplitude increases with increasing indium fraction and abruptly disappears at a critical time that depends on GaN thickness. We show that spatially localized, coherent acoustic phonon wave packets are generated via the photoexcited carriers and propagate into the samples modulating the reflectivity. Our results show that a system with strong built-in strain can be a very effective source for ultrafast acoustic phonon wave packets which can be used as a powerful probe for nanoscale structures.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.1488693
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2002
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
    Online Resource
    Online Resource
    Interband magneto-spectroscopy in InSb square and parabolic quantum wells
    AIP Publishing ; 2015
    In:  Journal of Applied Physics Vol. 117, No. 21 ( 2015-06-07)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 117, No. 21 ( 2015-06-07)
    Abstract: We measure the magneto-optical absorption due to intersubband optical transitions between conduction and valence subband Landau levels in InSb square and parabolic quantum wells. InSb has the narrowest band gap (0.24 eV at low temperature) of the III–V semiconductors leading to a small effective mass (0.014 m0) and a large g–factor (−51). As a result, the Landau level spacing is large at relatively small magnetic fields ( & lt;8 T), and one can observe spin-splitting of the Landau levels. We examine two structures: (i) a multiple-square-well structure and (ii) a structure containing multiple parabolic wells. The energies and intensities of the strongest features are well explained by a modified Pidgeon-Brown model based on an 8-band k•p model that explicitly incorporates pseudomorphic strain. The strain is essential for obtaining agreement between theory and experiment. While modeling the square well is relatively straight-forward, the parabolic well consists of 43 different layers of various thickness to approximate a parabolic potential. Agreement between theory and experiment for the parabolic well validates the applicability of the model to complicated structures, which demonstrates the robustness of our model and confirms its relevance for developing electronic and spintronic devices that seek to exploit the properties of the InSb band structure.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4921293
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 4
    Online Resource
    Online Resource
    Theoretical and experimental studies of cyclotron resonance in p-type InAs and InMnAs at ultrahigh magnetic fields
    AIP Publishing ; 2003
    In:  Journal of Applied Physics Vol. 93, No. 10 ( 2003-05-15), p. 6897-6899
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 93, No. 10 ( 2003-05-15), p. 6897-6899
    Abstract: We report theoretical and experimental ultrahigh magnetic field cyclotron resonance (CR) studies of paramagnetic p-type InAs and InMnAs. Experimental results are compared with an 8 band Pidgeon–Brown model which includes (i) the wave vector dependence of the electronic states along the magnetic field, and (ii) s–d and p–d exchange interactions with Mn ions. CR spectra are computed using Fermi’s golden rule. Results show two strong peaks associated with heavy and light hole transitions. Line shapes of the transitions provide information on the carrier densities.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1556157
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2003
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 5
    Online Resource
    Online Resource
    Photocurrent spectroscopy of In x Ga1− x As/GaAs multiple quantum wells
    AIP Publishing ; 1989
    In:  Applied Physics Letters Vol. 54, No. 22 ( 1989-05-29), p. 2230-2232
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 54, No. 22 ( 1989-05-29), p. 2230-2232
    Abstract: Photocurrent spectra of InxGa1−xAs/GaAs multiple quantum well structures grown by molecular beam epitaxy are studied in the presence of electric fields perpendicular to the heterointerface. Several Δn=0 allowed and Δn≠0 forbidden excitonic transitions are observed. Both negative and positive shifts of exciton transitions are found. Good agreement is found between the photocurrent observations and calculations using a multiband effective-mass approach, taking into account the strain-induced splitting.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.101132
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1989
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 6
    Online Resource
    Online Resource
    Absorptive electro-optic spatial light modulators: Effect of well profile on device performance
    AIP Publishing ; 1989
    In:  Applied Physics Letters Vol. 55, No. 10 ( 1989-09-04), p. 930-932
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 55, No. 10 ( 1989-09-04), p. 930-932
    Abstract: We report the effect of well profile on the performance of absorptive electro-optic spatial light modulators based on multiquantum well structures. In particular we calculate the variation in exciton oscillator strength and the absorption coefficient at the signal wavelength as a function of applied electric field. For a monochromatic source at 1572 meV, for example, we consider modulators based on square, parabolic, and asymmetric triangular GaAs-AlxGa1−xAs quantum wells and find that at zero field the exciton oscillator strengths are comparable but that superior performance is obtained using asymmetric triangular wells. These conclusions hold even assuming fairly large exciton linewidths in triangular wells.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.101727
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1989
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 7
    Online Resource
    Online Resource
    Absorptive electro-optic spatial light modulators with different quantum well profiles
    AIP Publishing ; 1990
    In:  Journal of Applied Physics Vol. 68, No. 10 ( 1990-11-15), p. 5348-5356
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 68, No. 10 ( 1990-11-15), p. 5348-5356
    Abstract: We present a theory of absorptive electro-optic spatial light modulators based on GaAs/AlGaAs multi-quantum well structures using arbitrary potential well profiles. In particular, we consider three different quantum well profiles: square, parabolic, and asymmetric triangular. We calculate the transition energies, oscillator strengths and absorption co-efficients of the lowest-lying heavy- and light-hole excitons as a function of well width and electric field using a variational approach assuming decoupled valence subbands. For illustrative purposes we select the photon energy of the monochromatic source to be modulated at 1572 meV and aluminum concentration in the barriers to be 0.3. For the sake of comparison among the various modulators with different quantum well profiles we assume that this photon energy coincides with the lowest-heavy-hole exciton transition in the absence of an electric field. We find that the required well widths are 75 Å for the square well, 174 Å for the parabolic well, and 676 Å for the asymmetric triangular well. At zero electric field the values of the exciton oscillator strengths in all three quantum well systems are comparable. However, superior performance in terms of higher contrast ratio is obtained in the case of modulators based on asymmetric triangular wells. For instance, in the case of a square well with excitonic linewidth of 3 meV, a field of approximately 50 kV/cm is required to achieve a 30% decrease in absorption. On the other hand, the field required to achieve the same change in absorption in a parabolic well is 35 kV/cm and in an asymmetric triangular well is −7 kV/cm. The contrast ratio at an electric field of −20 kV/cm is 6.7 for an asymmetric triangular well and 1.02 for a square well in a multi-quantum well sample where the contacts are 2 μm apart.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.347030
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1990
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 8
    Online Resource
    Online Resource
    Theory of the effect of magnetic field on the excitonic photoluminescence linewidth in semiconductor alloys
    AIP Publishing ; 1991
    In:  Journal of Applied Physics Vol. 70, No. 3 ( 1991-08-01), p. 1866-1868
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 70, No. 3 ( 1991-08-01), p. 1866-1868
    Abstract: We report a calculation on the effect of the magnetic field on the excitonic photoluminescence linewidth in intentionally undoped semiconductor alloys. We assume that the dominant mechanism for line broadening is due to the potential fluctuations caused by the disorder of the components of the alloy. Variations in the local concentrations from the global value are accounted for by using statistical mechanical arguments developed by Lifshitz [Adv. Physics 13, 483 (1965)] and then related to the linewidth. When a magnetic field is applied to the system, the effective volume of the optical probe, namely, the exciton, is reduced, causing it to become more responsive to the statistical potential fluctuations. This results in the broadening of the photoluminescence line as a function of the magnetic field. Variation of the excitonic linewidth as a function of the magnetic field and alloy composition in AlxGa1−x As is presented.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.349509
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1991
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 9
    Online Resource
    Online Resource
    Excitonic photoluminescence line shape due to interfacial quality in quantum well structures in a magnetic field
    AIP Publishing ; 1991
    In:  Journal of Applied Physics Vol. 69, No. 7 ( 1991-04-01), p. 4056-4059
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 69, No. 7 ( 1991-04-01), p. 4056-4059
    Abstract: We present a theory correlating the excitonic photoluminescence linewidth in quantum wells with the microscopic structure of the interface in the presence of a magnetic field. The interface is described in terms of microscopic fluctuations δ1 and δ2 where δ1 is the local fluctuation in the well width and δ2 is the lateral correlated extent of the fluctuation. We use Lifshitz’s theory of disordered alloys to determine the probability distribution of fluctuations of the well size over the effective extent of the optical probe, namely, the exciton. The line shape is then calculated from this distribution. We have evaluated the fullwidth at half maximum (σ) for both the heavy-hole exciton and the light-hole exciton as a function of the well size and interface parameters δ1 and δ2 in the presence of a magnetic field in GaAs-Al0.3Ga0.7As and In0.53Ga0.47As-InP quantum well structures. We find that for a given set of values of well width and interface parameters, the application of the magnetic field reduces the effective size of the exciton and thus increases the linewidth.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.348416
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1991
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 10
    Online Resource
    Online Resource
    Optical properties of free-standing silicon quantum wires
    AIP Publishing ; 1992
    In:  Applied Physics Letters Vol. 60, No. 20 ( 1992-05-18), p. 2525-2527
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 60, No. 20 ( 1992-05-18), p. 2525-2527
    Abstract: We present theoretical studies of the optical properties of free-standing Si quantum wires, using an empirical tight-binding model which includes d orbitals and second-neighbor interactions. The excitonic effects are included within the effective-mass approximation. The predicted exciton transition energy for a quantum wire with a width of 27 Å agrees with the observed luminescence for a sample of similar size. We found that the thermally averaged exciton oscillator strengths for quantum wires with widths around 8 Å can become comparable to that of bulk GaAs.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.106927
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1992
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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