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  • 1
    Electronic Resource
    Electronic Resource
    Photoluminescence properties of ZnS epilayers (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2803-2809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive study is reported of the photoluminescence properties of ZnS thin films between 1.6 and 320 K grown by metalorganic molecular beam epitaxy and chemical beam epitaxy on GaAs substrates. Both heavy- and light-hole free excitons were observed at low temperatures with linewidths of 7.0 and 5.3 meV, respectively, as well as donor- and acceptor-bound excitons and free-to-bound recombination along with their longitudinal optical (LO) phonon replicas. The free exciton emission was observed up to 320 K, and enabled the room temperature band gap of ZnS to be unambiguously determined as 3.723 eV. The temperature dependence of the peak position, intensity, and linewidth was well described by the conventional empirical relations and by Toyozawa's exciton line shape theory. The bound exciton peak positions were found to follow the temperature dependence of the band gap whereas the free-to-bound recombination feature was displaced by (1/2)kT above the band gap energy. Thermal quenching of the donor-bound exciton was described by a one-step quenching process with an activation energy of 14.4 meV. The self-activation (SA) center was also observed at 2.846 eV with a linewidth of 410 meV. The temperature dependence of the SA emission was well described by the configuration coordinate model. From the thermal broadening of the SA emission, an average phonon energy of 47.5 meV was determined, in good agreement with the LO phonon energy. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363937
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  • 2
    Electronic Resource
    Electronic Resource
    Photoluminescence properties of ZnGa2O4:Mn powder phosphors (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5691-5695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of a systematic photoluminescence study of ZnGa2O4:Mn powder phosphor are reported. At room temperature this phosphor exhibits bright green luminescence with a spectral peak at 2.46 eV and Commission International de l'Eclairage chromaticity coordinates of x=0.073 and y=0.696. At low temperatures the luminescence was found to consist of three components assigned to the 4T1–6A1 inner transition of the 3d electrons of Mn2+ ions located on three different sites of the host crystal. Selective excitation and lifetime measurements were used to investigate the assignment of these features. The photoluminescence lifetime showed a single exponential decay of about 4 ms and at T=1.6 K an optical-phonon-related fine structure [Ephonon=(8.2±0.2) meV] of the main photoluminescence line was observed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359627
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  • 3
    Electronic Resource
    Electronic Resource
    Donor-acceptor pair luminescence involving the iodine A center in CdTe (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5669-5674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence studies from 5 to 296 K have been performed on a series of iodine-doped CdTe epilayers grown by molecular beam epitaxy. The samples exhibit excess electron concentrations in the range from 8×1016 to 3×1018 cm−3. Bright edge emission is observed at 296 K from all samples. A deep-level band centered near 1.45 eV is observed at T〈210 K and increases in intensity with doping level. A correlation of growth parameters with photoluminescence data fits a model of the deep-level band being predominantly donor-acceptor pair recombination involving the shallow iodine donor (ITe) and the iodine A-center acceptor complex (VCd-ITe). Zero-phonon emission related to this pair recombination occurs at 1.470 eV at 5 K. Thermal quenching of the integrated intensity of this donor-acceptor band is described by activation energies of 15 and 125 meV corresponding to thermalization of electrons from shallow ITe donors to the conduction band and complete thermalization from the valence band to iodine A centers, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359623
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  • 4
    Electronic Resource
    Electronic Resource
    Selective excitation of an associate donor-acceptor pair complex in iodine-doped CdTe (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4544-4547 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Luminescence at 1.491 eV was detected at liquid-helium temperatures from CdTe epilayers heavily doped with iodine. The relatively sharp emission band (FWHM=4.4 meV) was observed under both above-band-gap and below-band-gap excitation. The intensity of the 1.491 eV emission was highly dependent on sample temperature and could only be detected below 45 K. Using the tunable output from a titanium:sapphire laser, selective excitation of this emission was performed to identify the recombination center. A localized mode of 36.5 meV, much larger than the 21.3 meV bulk CdTe mode, is associated with the defect center. We identify the defect as an associate donor-acceptor pair complex resulting from nearest neighbor cation (NaCd) and anion (ITe) point defects. The energy level associated with the (Na−Cd-I+Te) neutral associate pair is approximately 0.115 eV below the CdTe conduction band. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359416
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  • 5
    Electronic Resource
    Electronic Resource
    Theory of resonant tunneling in a variably spaced multiquantum well structure: An Airy function approach (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 614-623 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schrödinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented herein is easily extended to many layer structures where it is more accurate than other existing transfer matrix or Wentzel–Kramers–Brillouin (WKB) models. The transmission resonances are compared to the bound-state energies calculated for a finite square well under bias using either an asymmetric square-well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound-state energies. The calculations were then applied to a new superlattice structure, the variably spaced superlattice energy filter, which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338213
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  • 6
    Electronic Resource
    Electronic Resource
    The variably spaced superlattice electroluminescent display: A new high efficiency electroluminescence scheme (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 5410-5418 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a new, highly efficient dc electroluminescent display. A variably spaced superlattice scheme is suggested herein which can produce high-energy injection of electrons into a ZnSe:Mn active layer in which impact excitation of the Mn centers can occur. The device is predicted to operate at an applied external bias an order of magnitude less than the best dc electroluminescent device to date. The device is predicted to have comparable brightness, since it operates in the saturation regime. The improved efficiency stems from avoiding significant energy loss to phonons. The electrons sequentially tunnel through a multilayer stack under bias and emerge into the active layer at an energy equal to the conduction-band bending. The injection energy is chosen to coincide with the impact excitation energy of the Mn centers. Different device designs are presented and their performance is predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338281
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of annealing on the grain growth and luminescent properties of SrS:Cu blue phosphors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3999-4002 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Systematic studies of the postgrowth annealing of molecular beam epitaxial deposited SrS:Cu films are reported. In the as-grown SrS:Cu films, the grain size was small and the luminescence very weak. A step-annealing procedure in a H2S atmosphere was developed and found to be a very efficient way to improve the crystallinity and luminescent properties without damage to the low temperature glass substrate and insulator layer of the device. A model is presented in terms of the free energy of formation and the reaction kinetics of Cu with H2S. It was proposed that the weak luminescence in the as-grown films was attributed to Cu atoms segregated at the grain boundaries in the SrS film. The oxidation of atomic Cu by H2S and the diffusion of Cu+ into the SrS lattice during annealing were responsible for the grain growth and the improved luminescent properties. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370303
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  • 8
    Electronic Resource
    Electronic Resource
    Nucleation kinetics of molecular-beam epitaxially grown (001) ZnTe and CdTe surfaces (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5367-5372 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflection high-energy electron diffraction desorption studies have been performed on epitaxial (001) ZnTe surfaces. The desorption of Cd and Te were observed to follow a simple first-order rate law, while the desorption of Zn was more complicated. Activation energies of 3.7, 1.8, and 3.9 eV were found for Zn, Cd, and Te, respectively, on the ZnTe surface. The congruent evaporation temperature was determined to be 400 °C. The nucleation kinetics of (001) ZnTe and (001) CdTe are compared. A theoretical model was employed to predict a method for growing high-quality ZnxCd1−xTe .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343731
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  • 9
    Electronic Resource
    Electronic Resource
    Photoluminescence of n-type CdTe:I grown by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4541-4545 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Liquid helium temperature and temperature-dependent photoluminescence (PL) spectroscopy have been performed on highly n-type-doped CdTe:I films grown by molecular beam epitaxy. The samples were grown on 2° off (001) oriented bulk CdTe substrates at substrate temperatures from 170 to 250 °C, and exhibit room-temperature electron concentrations of 1×1017 cm−3. The brightest PL edge emission at liquid helium and room temperatures was observed from a sample grown at 210 °C. At T=5 K, the iodine donor radiative recombination was observed at 1.593 eV, corresponding to a donor ionization energy of 14 meV for the ITe substitutional donor, in agreement with the predicted hydrogenic donor ionization energy for CdTe. The thermal quenching behavior of the edge emission peak is a two-step process involving both 10 and 14 meV activation energies. These activation energies are related to the thermalization of the ITe donor from the ground state to the first excited state (1s→2s, 10 meV), and complete thermalization from the donor ground state to the conduction band (14 meV).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352798
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  • 10
    Electronic Resource
    Electronic Resource
    A two-component phosphor approach for engineering electroluminescence phosphors (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2398-2400 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electroluminescence (EL) properties of SrS:Cu, SrS:Ag, and SrS:Ag,Cu thin-film phosphors are reported. SrS:Cu and SrS:Ag are shown to exhibit very different EL properties with SrS:Cu possessing a luminance and efficiency of 30.8 cd/m2 and 0.2 lm/W, compared to SrS:Ag whose luminance and efficiency are 0.7 cd/m2 and 0.001 lm/W, respectively. In contrast, SrS:Ag,Cu exhibits the high luminance and efficiency of SrS:Cu, but the saturated chromaticity of SrS:Ag, which exhibits an excellent blue chromaticity of (0.17,0.15). The improved electroluminescent luminance, efficiency, and color purity of SrS:Ag,Cu are explained by the energy transfer from the Cu+ to Ag+ ions. These results suggest a concept to improve EL performance through the use of a class of two-component phosphors, which exhibit superior color, brightness, and excitation efficiency. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125026
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