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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for a magnetic hard gap in the density of states of a magnetic semiconductor near the metal insulator transition (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5750-5750 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A family of resistivity curves with carrier concentrations approaching the metal insulator transition is obtained in a single sample of the dilute magnetic persistent photoconductor Cd0.91Mn0.09Te:In. In zero applied magnetic field, these curves exhibit a cross-over from an exp[(T0/T)1/2] for variable range hopping with interactions to an exp(EH/T) form upon reducing temperature. The energy EH is associated with a hard gap in the density of states which is magnetic in origin. All of the data for different carrier concentrations are shown to scale on to a single curve.1 The localization length is found to have the same critical dependence as the electronic part of the dielectric constant which has been previously measured.2 In a magnetic field, the hard gap is suppressed, and only variable range hopping is observed. The orientation of the Mn spins by the carriers contributes both to the localization (bound magnetic polaron) and is the relaxation responsible for the hard gap. A large peak in the magnetoresistance is also understood within this model. The localization length ξ and hence T0=2.8e2/κξk and the resistivity are field dependent. The magnetic field first aids the BMP formation and then destroys it. The result is first a peak and then in some cases negative magnetoresistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353562
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of local magnetization of magnetotransport in Cd0.92Mn0.08Te:In (invited) (abstract) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5834-5834 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetically tuned insulator-metal transition in magnetic semiconductors is one of the most striking demonstrations of the interaction between localized magnetic moments and carriers.1 On the metallic side of the transition, it is believed that magnetotransport arises from electron-electron interactions in the presence of a giant Zeeman splitting of the conduction band. However, magnetotransport in the insulating phase is not well understood. The discovery of persistent photoconductivity in Cd1−xMnxTe:In2 has made it possible to control carrier concentration by illumination. This enables us to make transport measurements over a wide range of carrier concentrations in one single sample, ultimately leading to the phototuning of the Mott–Anderson transition in this magnetic semiconductor. In the present work, we report an investigation of magnetotransport and permittivity as a function of carrier concentration in Cd0.92Mn0.08Te:In(2×1018 cm−3). In the insulating phase, the resistivity shows an exp[(T0/T)1/2] temperature dependence, characteristic of variable range hopping in the presence of electron-electron interactions.3 Our results imply that magnetotransport is governed by local magnetization characteristic of the relevant length scale for the transport process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350126
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  • 3
    Electronic Resource
    Electronic Resource
    Persistent photoconductivity and DX centers in Cd0.8Zn0.2Te:Cl (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5827-5829 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transport measurements on large single crystals of Cd0.8Zn0.2Te:Cl indicate that Cl donors form DX centers in CdZnTe. We have observed persistent photoconductivity (PPC) with an annealing temperature Ta≈130 K. Hall-effect experiments indicate that the PPC arises from a persistent increase in the density of charge carriers; the saturation density is Nsat=6×1016 cm−3. The deep binding energy of the DX center is Ed=0.22 eV. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359648
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  • 4
    Electronic Resource
    Electronic Resource
    Lattice vibrations of cadmium manganese telluride alloys (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 310-314 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflectivity spectra in the reststrahlen region (100–250 cm−1) are presented for bulk zinc blende Cd1−xMnxTe crystals at 2, 50, and 300 K and for x=0 to 0.64, covering nearly the entire possible composition range for cubic structure. Kramers-Kronig analysis gives the transverse and longitudinal phonon frequencies. The Lorentz model confirms these results and also gives mode strengths and damping constants. Compositional dependence of the phonon energies is predicted by the random element isodisplacement model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341428
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  • 5
    Electronic Resource
    Electronic Resource
    Optical studies of Cd0.9Mn0.1Te doped with Au, As, Cu, and P acceptors (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2396-2401 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical absorption and photoluminescence measurements were made on Cd0.9Mn0.1Te doped with As, P, Cu, and Au. Shallow acceptor ionization energies were determined as: 108 meV for P; 115 meV for As; 170 meV for Cu; and 180 meV for Au. These energies are larger than those for CdTe due to the formation of bound magnetic polarons. Self-consistent numerical calculations of the bound magnetic polarons are made for As and P dopants. The absorption spectra below 0.5 eV were separated into contributions from acceptor photoionization, inter- and intraband transitions, and free-hole absorption. Acceptor concentrations in the 1017 cm−3 range were found for As and P doping; however, Cu and Au were found to produce high compensation (〈1012 cm−3). Mechanisms for this behavior are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341058
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  • 6
    Electronic Resource
    Electronic Resource
    Electroreflectance study of Hg1−xMnxTe in the E1 and E1+Δ1 energy regions (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1135-1138 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report electrolyte electroreflectance studies of the ternary semimagnetic semiconductor Hg1−xMnxTe for compositions below x=0.2. The dependence of E1 and E1+Δ1 transition energies on the composition was determined on the basis of the low field approximation. The present results are compared and discussed in relation to experimental data obtained previously and the theoretical predictions reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337357
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical and optical properties of P- and As-doped Cd1−xMnxTe (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1352-1362 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The introduction of phosphorus and arsenic dopants into bulk Cd1−xMnxTe crystals grown by the Bridgman–Stockbarger technique has been studied with respect to the resulting electrical and optical properties. Uncompensated acceptor concentrations as high as 1015–1016 cm−3 are obtained. Samples with a Mn composition in the range 0.10〈x〈0.30, both as-grown and annealed, are studied. Hall-effect and resistivity measurements are used to determine carrier concentrations, mobilities, and acceptor activation energies. A combination of room-temperature transmittance and reflectance measurements over the spectral range from the ultraviolet to the far infrared has been used to gain information concerning structural quality and point defects. Low-temperature photoluminescence measurements (1.6–5 K) are used to determine optical quality and excitonic energies. The effect of alloy broadening on luminescence linewidth is calculated and compared with measured values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339638
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  • 8
    Electronic Resource
    Electronic Resource
    Substitutionality of Ge atoms in ion implanted AlSb (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2406-2408 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The substitution of Ge atoms into ion implanted AlSb is investigated by extended x-ray absorption fine structure spectroscopy. Our results reveal that in the as-implanted material, the implanted Ge atoms are equally distributed between two specific sites, one surrounded by Al atoms and the other surrounded by Sb atoms. After annealing at 750 °C for 5 s, the coordination number of the Ge atoms increases from ∼3 to ∼4 indicating solid phase regrowth of the implantation induced amorphous surface layer. Moreover, in the annealed AlSb, the substitution of Ge atoms into the Al sublattice dominates with an estimated GeAl]:[GeSb]∼0.8:0.2. These results suggest that Ge atoms act preferentially as donor species in AlSb. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113955
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  • 9
    Electronic Resource
    Electronic Resource
    Persistent holographic absorption gratings in AlSb:Se (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 735-737 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoquenching of DX-like defects in heavily doped AlSb:Se is used to write persistent volume absorption holograms. Read-out diffraction efficiencies of ∼0.5% were observed in samples 280 μm thick. The optical gratings are metastable, and semipermanent at liquid nitrogen temperatures, and are reversibly erased by heating the crystal above 140 K. The activation energy of regeneration of the stable DX state is obtained by measuring the decay times of the diffracted signal for temperatures between 100 and 116 K. We obtain a regeneration energy of 180 meV. Larger regeneration energies are important for eventual application of this material class to holographic optical memories. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116725
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  • 10
    Electronic Resource
    Electronic Resource
    Large photoinduced persistent optical absorption in selenium doped AlSb (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 395-397 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature, T〈90 K, illumination transfers transparent, single crystals of AlSb doped with Se to a metastable state characterized by a high optical absorption approaching 200 cm−1. The enhanced absorption spectrum extends from 0.1 to 1.5 eV and consists of a double band structure with peaks at 0.2 and 0.5 eV. It is induced by photons with a threshold energy of about 1 eV. It is persistent, i.e., it shows no measurable decay after switching off the excitation. The low absorption state is thermally recovered at 100 K. The persistent absorption is a manifestation of a DX-type bi-stability of the Se donor. The 0.2 and 0.5 bands are, respectively, due to the photoionization of electrons from the metastable hydrogenic donor level to X1 and X3 conduction band minima. A large binding energy of the Se donor is essential for the observation of persistent absorption and a lack of any free-electron related effects. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114640
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