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  • 1
    Electronic Resource
    Electronic Resource
    Shubnikov–de Haas oscillations on as-grown and annealed molecular-beam-epitaxy-grown Hg1−xCdxTe alloys doped with indium (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 216-225 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transverse resistivity ρxx, longitudinal resistivity ρzz, and Hall resistivity ρxy on heavily indium-doped as-grown and annealed Hg1−xCdxTe (0.24〈x〈34) alloys in a magnetic field up to 12 T and temperature range 1.2–25 K have been measured. The as-grown and annealed samples show good quality Shubnikov–de Haas oscillations in which the effective masses m*, free-electron densities nSdH, and Dingle temperatures TD are extracted. The deduced m* and nSdH from the as-grown and annealed samples are in good agreement within 12%. However, there are considerable improvements in the low field Hall mobility μH (a maximum 54% increase) and a reduction in TD (a maximum 65% decline) in the annealed samples. Analysis at low field seems to indicate that broadening due to an inhomogeneous impurity distribution contributes to TD in addition to the partial cancellation produced by different frequencies of oscillations. An estimate of the average values of an electron density fluctuation Δn/n and its spatial extent ΔL based only on TD and Hall mobility temperature Tμ is presented. The deduced ΔL is in the order of mean free path l. This, therefore, can limit μH and the values of l and ΔL and this indicates that if there is an inhomogeneous distribution of indium donor, high-temperature annealing tends to homogenize the distribution of indium donors by diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353885
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  • 2
    Electronic Resource
    Electronic Resource
    Minority-carrier lifetime in p-type (111)B HgCdTe grown by molecular-beam epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5195-5199 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of electron lifetime have been carried out on unintentionally doped layers of (111)B Hg1−xCdxTe (0.216〈x〈0.320), p-type as-grown by molecular-beam epitaxy. The temperature dependence of the bulk lifetime is explained in terms of the Shockley–Read recombination mechanism for the extrinsic region. The samples have shown a deep level close to midgap. The surface recombination seen in two of the samples is accounted for. Some samples show clearly Auger-limited recombination at high temperatures. From the values of τn0 and τp0 of two samples the trap level appears to have a donorlike character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347061
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  • 3
    Electronic Resource
    Electronic Resource
    Shubnikov–de Haas oscillations on molecular-beam-epitaxy-grown Hg1−xCdxTe alloy doped with indium (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4326-4331 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shubnikov–de Haas oscillations on the transverse resistivity ρxx and longitudinal resistivity ρzz of as-grown indium-doped alloys of Hg1−xCdxTe (0.24〈x〈0.34) grown by molecular-beam epitaxy on (111)B and (100) growth directions are observed in the temperature range from 1.2 to 25 K and in fields up to 12 T. The n-type density from the periodicity, the effective mass m* from the temperature dependence of the amplitude, and the Dingle temperature TD are determined from ρxx and ρzz oscillations. The oscillations establish the high Hall density which is found at low fields. The TD in ρxx is found to be higher in comparison to TD in ρzz. However, this difference decreases as the Hall density increases. The TD discrepancy is probably due to greater inhomogeneity in the plane of the layer. The TD is higher than the temperature calculated from the weak-field Hall mobility. The density and effective mass are used to calculate the energy band gap, Fermi energy, and the band-edge effective mass. The calculated energy band gaps are in good agreement with the reported results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349112
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetotransport in type-III Hg1−xZnxTe-CdTe superlattices (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1151-1160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetotransport experiments on several n-type Hg1−xZnxTe-CdTe superlattices reveal the existence of two species of charge carriers which dominate in low and in high magnetic fields. These superlattices exhibit low-magnetic-field Shubnikov–de Haas oscillations and Hall plateaus in one superlattice. They also exhibit a metal-insulator transition due to an energy gap induced by the high magnetic fields. The induced energy gap is estimated using a simplified parallel-conduction model. When most of the electrons in the superlattices have been magnetically frozen out, a second species of charge carriers starts dominating the charge transport. The second species of charge carriers shows large amplitude Shubnikov–de Haas oscillations and Hall plateaus. The standard determination of effective masses, mobilities, and carrier densities from the Shubnikov–de Haas oscillations in low and in high magnetic fields also confirms the presence of two species of charge carriers of different origin. It is proposed that the high-magnetic-field Shubnikov–de Haas oscillations are due to electrons residing at the buffer-superlattice interface on the superlattice side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354915
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  • 5
    Electronic Resource
    Electronic Resource
    Hall electron density and mobility in HgCdTe alloys with anomalous behavior of the Hall coefficient in weak magnetic field (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1096-1099 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is difficult to extract unique values of the Hall electron density, nH, and Hall mobility, μH, in indium-doped Hg1−xCdxTe alloys usually in a region of weak magnetic fields where the Hall coefficient RH behaves anomalously. Since this is also the field region where the weak magnetic field condition of semiclassical transport equations is valid, derivatives of Hall resistivity ρxy(B) and the ratio (Hall angle) of ρxy(B) and transverse resistivity ρxx(B) with respect to the field are used to determine unique values of the weak magnetic field nH and μH. This analysis reduces to calculating the slopes of ρxy(B) and ρxy(B)/ρxx(B) in the region of weak magnetic fields where linearity is observed. The conductivity, σ0, determined from the ratio of the slopes is compared to the zero magnetic-field experimental value. The conductivities agree to within 10%, indicating that nH is constant in contrast to the RH result. The values of nH determined from the slopes are in very good agreement with the values of nH determined from a high magnetic field RH and from the period of Shubnikov–de Haas oscillations in heavily doped alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354958
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  • 6
    Electronic Resource
    Electronic Resource
    Growth modes and microstructures of ZnO layers deposited by plasma-assisted molecular-beam epitaxy on (0001) sapphire (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5115-5119 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy and high resolution x-ray diffraction are used to characterize defects in ZnO layers grown by plasma-assisted molecular-beam epitaxy on (0001) sapphire. Two- and three-dimensional types of growth modes are described and the observed mosaic structure is analyzed in each case. It is found that two-dimensional layers exhibit a roughness as low as 6 nm. Their subdomains have small lateral coherence lengths and a mean in-plane misorientation of ±0.4°, leading to an important dislocation density of 1–4×1010 cm−2. On the contrary, it is demonstrated that, through numerous interactions between dislocations, the three-dimensional growth mode leads to a better structural quality with a larger lateral coherence length and a smaller in-plane mosaic spread of ±0.07°. The total dislocation density is consequently reduced by 1 order of magnitude down to 3–5×109 cm−2 and the radical modification of the structure results in a change of the dislocation distribution. Our results thus demonstrate that two-dimensional growth mode and low full width at half maximum for symmetric x-ray diffraction are a not reliable indicator of a good structural quality. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412572
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  • 7
    Electronic Resource
    Electronic Resource
    MBE grown CdTe photoconductor array detector for x-ray measurements : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2320-2323 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A photoconductor array was made using molecular-beam epitaxy (MBE) grown CdTe. CdTe has been found to be an excellent material for high-energy photon detection. The objective is to develop an array detector with high efficiency and fast response toward x rays. There is considerable interest in the development of new x-ray detectors for use in the new synchrotron-radiation sources. Photoconductor arrays with gaps ranging from 5 to 50 μm between elements and 100 μm pitch size have been fabricated. The temporal response of the detectors was measured using 100 fs Ti:sapphire laser pulses. The temporal response of the photoconductor arrays is as fast as 21 ps rise time and 38 ps full width half maximum (FWHM). Spatial and energy responses were obtained using x rays from rotating anode (ANL) and synchrotron-radiation sources (NSLS, beam line X-18 B). The spatial resolution of the photoconductor obtained was 75 μm FWHM, for a 50 μm beam size. The best results were obtained for those arrays with the best crystal qualities. Linear response up to an energy of 15 keV was observed. Also observed was that a substantial number of x-ray photons were effectively absorbed within the MBE CdTe layer. The array detector did not show any evidence of radiation damage after x-ray exposures of several days. When the detector is cooled to 230 K the signal-to-noise ratio is improved by more than an order of magnitude. These results demonstrate that MBE grown CdTe is a suitable choice to meet the detector requirements for synchrotron-radiation applications. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145676
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  • 8
    Electronic Resource
    Electronic Resource
    Transient picosecond/subpicosecond Raman scattering studies of nonequilibrium electron distributions and phonons in CdTe (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3840-3843 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonequilibrium electron distributions and phonons in CdTe have been studied by transient picosecond/subpicosecond Raman spectroscopy at T=300 K. Our experimental results show that for photoexcited electron–hole density of n(approximately-equal-to)1018 cm−3, the electron distributions can be reasonably well described by Fermi–Dirac distribution functions with effective electron temperature substantially higher than the lattice temperature. From an ensemble Monte Carlo analysis of the nonequilibrium phonon population as a function of photoexcited electron–hole pair density, the LO phonon lifetime in CdTe has been deduced to be τ(approximately-equal-to)0.75±0.25 ps. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363338
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  • 9
    Electronic Resource
    Electronic Resource
    Structural and optical characterization of ZnSe single crystals grown by solid-phase recrystallization (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2983-2989 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate by high-resolution x-ray diffraction (HRXRD), temperature-dependent photoluminescence (PL) and reflectivity spectroscopies, and low-temperature selective-photoluminescence spectroscopy ZnSe single crystals grown by solid-phase recrystallization. HRXRD reveals the high structural perfection of the samples which exhibit rocking-curve linewidths in the 15–20 arcsec range. The low-temperature PL spectra are dominated by the so-called Ideep1 excitonic line, a neutral-acceptor bound-exciton line I1, the free-exciton emission FX, and the n=2 excited state of FX. We identify the main residual impurities to be Li acceptors. Donor–acceptor pair bands are very hardly detected at low temperature which indicates a low donor content. A major characteristics of these samples is the quasi-absence of any Cu-related deep emission which generally plagues the PL spectra of bulk ZnSe. Consequently, Ideep1 is ascribed to Zn-vacancy–donor complexes. Finally, from the temperature dependence of the PL emission and reflectivity, the band-gap energy of bulk ZnSe is found to linearly shrink with the temperature above 80 K at a rate of −4.3×10−4 eV K−1. The room-temperature gap is estimated to 2720±2 meV. Our results indicate that solid-phase recrystallization produces ZnSe samples with the highest structural quality and purity achievable at present time. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363155
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  • 10
    Electronic Resource
    Electronic Resource
    Carrier recombination in indium-doped HgCdTe(211)B epitaxial layers grown by molecular beam epitaxy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1005-1009 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the recombination mechanisms of minority carrier lifetime in indium-doped layers of (211)B Hg1−xCdxTe(x ≈ 23.0% ± 2.0%)n-type grown by molecular beam epitaxy. Measured lifetimes were explained by an Auger limited band-to-band recombination process in this material, even in the extrinsic temperature region. Frequently, in some of the layers, a combination of the band-to-band recombination mechanisms together with recombination at the Shockley–Read single level 33 to 45 meV below the conduction band was necessary to explain the measured data. Results indicate that these defects have acceptorlike characteristics and their origin is related to Hg vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356506
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