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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2656-2665 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and optical properties of bulk CdTe:In have been studied by means of van der Pauw-Hall-effect measurements and low-temperature photoluminescence (PL). As-grown, the bulk CdTe:In samples exhibited high resistivity (ρ〉108 Ω cm). Following a high-temperature anneal at 900 °C in a Cd overpressure, the CdTe samples became n-type (n∼1016 −1017 cm−3 at 300 K). The carrier concentration was found to depend on the anneal time. The PL spectra from as-grown samples are dominated by edge emission at 1.583–1.584 eV, the nature of which is determined from the optical measurements. As a result of the anneal, PL emission above 1.606 eV (the band gap of CdTe at 4.5 K) is observed. Excitation PL measurements, along with studies of the temperature and power dependencies of the PL emissions from the annealed samples, suggest an increase in band gap to 1.632 eV has occurred, which we believe is due to the incorporation of interstitial Cd into the lattice. Our study provides a correlation between the electrical and optical properties of bulk CdTe:In which, upon annealing, may be used as a conducting II-VI substrate in epitaxial film growth.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3314-3318 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence and optical absorption spectroscopies have been used to study bulk ZnGeP2. Two sharp zero-phonon lines with opposite polarizations are resolved in emission at 1.7849 eV (at 70 K) and 1.7784 eV (at 5 K), respectively. Thermalization occurs between these two lines, suggesting a split excited state of the center. Considerable structural detail is resolved in the vibronic sidebands of these lines, revealing phonon energies of 6.3±0.1 meV and 43.7±0.1 meV. Similar phonon energies are resolved in low-temperature absorption spectra. These results for ZnGeP2 are explained by a model of radiative recombination of excitons bound to an isoelectronic defect center. The observed polarization behavior of the sharp-line spectra can be produced by the built-in tetragonal distortion along the c axis associated with the chalcopyrite structure. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 622-624 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR), photoluminescence, and infrared optical absorption have been used to investigate a ZnO crystal before and after a thermal anneal for 1 h in air at 900 °C. The sample was an undoped high quality crystal grown by the chemical vapor transport method. In addition to shallow donor impurities, the crystal contained trace amounts of copper ions. Prior to the thermal anneal, these ions were all in the Cu+ (3d10) state and the observed luminescence at 5 K, produced by 364 nm light, consisted of a broad structureless band peaking at 500 nm. After the high-temperature anneal, the Cu2+ (3d9) EPR spectrum was observed and the luminescence had changed significantly. The emission then peaked near 510 nm and showed structure identical to that reported by Dingle [Phys. Rev. Lett. 23, 579 (1969)]. Our data reaffirm that the structured green emission in ZnO is associated with Cu2+ ions. We suggest that the unstructured green emission (observed before the high-temperature anneal) is donor–acceptor pair recombination involving the Cu+ acceptors. © 2002 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 170-172 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the successful p-type doping of CdTe films with arsenic using the photoassisted molecular beam epitaxy growth technique. These doped epilayers were grown at substrate temperatures as low as 180 °C. The room-temperature hole concentrations in the CdTe:As layers ranged from 7×1015 to 6.2×1018 cm−3 as determined by van der Pauw–Hall effect measurements. We propose a doping mechanism responsible for the high p-type doping levels observed in the films. The arsenic acceptor ionization energy was found to ∼58–60 meV using low-temperature photoluminescence measurements.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2026-2028 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the first observation of stimulated emission from Hg-based quantum well structures in which the active region is a HgCdTe superlattice. The laser structures were grown on (100) CdZnTe substrates photoassisted molecular beam epitaxy. Cleaved laser cavities were optically pumped using the 1.06 μm output from a cw Nd:YAG laser. Stimulated emission cavity modes were seen at cw laser power densities as low as 3.4 kW/cm2 and at temperatures ≥ 60 K.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 556-558 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR) has been used to detect Ni+ impurities substituting for Ag+ ions in a single crystal of AgGaSe2. The observed EPR spectrum has axial symmetry about the c axis of the crystal and is described by g(parallel)=2.635 and g⊥=2.241. A partially resolved hyperfine pattern in the c-axis spectrum is consistent with equivalent interactions with four I=3/2 nuclei (e.g., 69,71Ga). The concentration of Ni+ ions in the undoped crystal was approximately 7×1017 cm−3. These substitutional Ni+ impurity ions are suggested to be responsible for the polarized 2.2 μm absorption band that is presently limiting the use of AgGaSe2 as a 2 μm pumped optical parametric oscillator with mid-infrared output. © 1996 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 537-541 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A noncontact, nondestructive optical technique with potential to measure the acceptor impurity concentrations in bulk CdTe and Cd1−xZnxTe alloys is described here. The technique, called optical quenching, uses an infrared light source in conjunction with the above-band-gap excitation beam used in standard photoluminescence spectroscopy. The quenching, or decrease, of acceptor-bound exciton emission is related to the incident infrared beam flux. The rate at which the infrared photons ionize neutral acceptors can be used to determine relative concentrations of the substitutional centers. We have applied this technique to the copper acceptor-bound exciton in CdTe and Cd1−xZnxTe bulk samples. The 1.064 μm output from a Nd:YAG laser provided near-resonant absorption with the copper acceptor level. Relative copper concentrations in the range from 4×1014 to 1×1016 cm−3 were obtained. These values agree reasonably well with sample comparisons based on atomic absorption data.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4544-4547 
    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.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6866-6871 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low temperature (∼5 K) photoluminescence spectroscopy was performed on undoped CdTe epilayers grown by molecular beam epitaxy on (211)B oriented bulk GaAs substrates at substrate temperatures ranging from 230 to 275 °C. The emission spectra from all samples studied contained evidence of the diffusion of gallium and arsenic atoms from the substrate. A broad, low amplitude emission band observed at 1.594 eV was related to the GaCd donor level in CdTe. Donor-acceptor pair recombination observed at 1.51 eV was due to the substitutional GaCd donor and AsTe acceptor. The level of compensation in the CdTe layers was determined from the energy shift of the donor-acceptor emission peak with excitation power, with the lowest degree of compensation observed in a sample grown at 230 °C. In addition, a bright emission peak was observed at 1.47 eV. This peak, which had been observed previously in homoepitaxial and heteroepitaxial growth of CdTe, was related to electron-hole recombination of a structural defect in the CdTe/GaAs epilayers with an electronic binding energy of ∼130 meV.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 976-980 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystals of strontium barium niobate (Sr0.61Ba0.39Nb2O6), normally referred to as SBN:61, have been investigated using optical absorption, micro-Raman, photoluminescence, and electron paramagnetic resonance (EPR) techniques. Both undoped and cerium-doped (nominally 0.01 to 0.10% Ce) samples were included in the study. A broad optical absorption band centered near 490 nm and extending to the band edge near 380 nm is observed at room temperature in the Ce-doped crystals. Additional absorption, which we assign to iron, occurs just below the band edge in some of the samples. Photoluminescence data were taken at room temperature. Sharp emission bands at 545 and 650 nm are assigned to Er3+, an emission band at 755 nm is assigned to Ho3+, and a broader emission band extending from 700 to 850 nm is assigned to Cr3+. The SBN:61 crystals strongly absorb 9.4 GHz microwaves. To minimize the effect of these microwave losses, the EPR data were taken near 7 K. A broad isotropic EPR line due to Ce3+ ions is observed at g=0.9 in the Ce-doped samples. Additional isotropic EPR lines due to Fe3+ ions are observed at g=9.35 and g=4.10. © 1995 American Institute of Physics.
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