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  • 1
    Electronic Resource
    Electronic Resource
    Contactless measurement of the conductivity of II–VI epitaxial layers by means of the partially filled waveguide method (1992)
    Springer
    Applied physics 55 (1992), S. 279-288 
    Details
    ISSN: 1432-0630
    Keywords: 72.20.−i ; 72.80.Ey ; 78.70.Gq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report the contactless determination of the conductivity, the mobility and the carrier concentration of II–VI semiconductors by means of the technique of the partially filled waveguide at a microwave frequency of 9 GHz. The samples are CdHgTe epitaxial layers, grown on CdZnTe substrates by molecular beam epitaxy. The conductivity is determined from the transmission coefficient of the sample in the partially filled waveguide. For the analysis of the experimental data, the complex transmission coefficient is calculated by a rigorous multi-mode matching procedure. By varying the conductivity of the sample, we obtain an optimum fit of the calculated data to the experimental results. Comparison with conductivity data determined by the van der Pauw method shows that our method allows to measure the conductivity with good accuracy. The behaviour of the transmission coefficient of the sample is discussed in dependence on the layer conductivity, the layer thickness and the dielectric constant of the substrate. The calculations require to consider in detail the distribution of the electromagnetic fields in the sample region. The usual assumption of a hardly disturbed TE10 mode cannot be used in our case. By applying a magnetic field in extraordinary Voigt configuration, galvanomagnetic measurements have been carried out which yield the mobility and thus the carrier concentration. These results are also in good agreement with van der Pauw transport measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348398
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanisms of molecular beam epitaxial growth of (001) HgTe (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 748-751 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on an investigation of the growth mechanisms of HgTe using a combination of reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The experiments were carried out on untilted (001) CdTe substrates. Growth rates were determined from RHEED intensity oscillations of the (00) specular spot reflection. The amplitude of these oscillations decrease with increasing substrate temperature. Above 178 °C no RHEED oscillations could be measured. Upon reducing the sample temperature below 178 °C these oscillations could again be observed. This cyclic behavior could be induced several times for each sample, indicating a reversible change in the growth mechanism. In order to correlate the surface structure with RHEED observations, several samples have been investigated with STM. Thus, it could be confirmed that a temperature dependent transition occurs during the MBE growth of HgTe from the island growth mode below the critical temperature of 178 °C to a step flow mode above this temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362682
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  • 3
    Electronic Resource
    Electronic Resource
    p-type doping of CdTe with a nitrogen plasma source (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2343-2346 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here on the growth and the characterization of p-type CdTe grown by molecular beam epitaxy on (001) Cd0.96Zn0.04Te substrates. Nitrogen has been used as a dopant, which is activated in an electron cyclotron resonance plasma source. The carrier concentration was determined using a C/V profiler. Nitrogen has been successfully incorporated substitutionally and hole densities up to 2.6×1017 cm−3 have been achieved. In addition we present data from x-ray diffraction and photoluminescence, which demonstrate the effect of self-compensation on the nitrogen-doped CdTe layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361160
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  • 4
    Electronic Resource
    Electronic Resource
    Optical properties of Zn1−xMgxSySe1−y epitaxial layers for blue-green laser applications (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5377-5380 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The refractive index and the E0 energy gap has been determined for a number of Zn1−xMgxSySe1−y alloys with x≤0.3 and y≤0.3 at temperatures between 5 and 300 K. It has been shown that the refractive index can be empirically expressed as a function of the E0 energy gap. Furthermore we have determined the temperature dependence of the E0 energy gap and hence the temperature dependence of the refractive index for these alloys. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359226
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature dependence of the energy gap of zinc-blende CdSe and Cd1−xZnxSe epitaxial layers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6861-6863 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the energy gap of zinc-blende CdSe and Cd1−xZnxSe has been determined over the entire range of composition from optical transmission and reflection measurements at temperatures between 5 and 300 K. The experimental results can be expressed by the following modified empirical Varshni formula, whose parameters are functions of the composition x: Eg(x,T)=Eg(x,0)−β(x)T2/[T+γ(x)]. Eg(x,0) exhibits a nonlinear dependence on composition, according to Eg=Eg(0,0)(1−x)+Eg(1,0)x−ax(1−x). The parameters β(x) and γ(x) can be expressed by β(x)=β(0)(1−x)+β(1)x+bx(1−x) and γ(x)=γ(0)(1−x)+γ(1)x. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363753
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  • 6
    Electronic Resource
    Electronic Resource
    The growth and structure of short period (001) Hg1−xCdxTe-HgTe superlattices (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2486-2493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular beam epitaxially grown short period (001) Hg1−xCdxTe-HgTe superlattices have been systematically investigated. Several narrow well widths were chosen, e.g., 30, 35 and 40 A(ring), and the barrier widths were varied between 24 and 90 A(ring) for a particular well width. Both the well width and the total period were determined directly by means of x-ray diffraction. The well width was determined by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier widths we have been able to set an upper limit on the average Cd concentration of the barriers, x¯b, by annealing several superlattices and then measuring the composition of the resulting alloy. x¯b was shown to decrease exponentially with decreasing barrier width. The structure of a very short period superlattice, i.e., 31.4 A(ring), was also investigated by transmission electron microscopy, corroborating the x-ray diffraction results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354687
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxial growth and evaluation of intrinsic and extrinsically doped Hg0.8Cd0.2Te on (100) Cd0.96Zn0.04Te (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3305-3312 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural and electrical properties of (100) Hg1−xCdxTe epilayers grown by molecular beam epitaxy have been systematically investigated for different Hg/Te flux ratios. The hillock density, electron concentration and the electron mobility depend strongly on the Hg/Te flux ratio. A minimum in the hillock density correlates well with the highest mobilities and the lowest concentrations. As is well known electrical properties are strongly influenced by structural defects. Structural defects such as twins and defects due to nonstoichiometry can be largely reduced by optimizing the Hg/Te flux ratio. It is shown that an optimum Hg/Te flux ratio exists within a narrow range between 270 and 360 at the growth temperature of 180 °C, in contrast with the larger range of the Hg/Te flux ratio over which single crystalline growth could be maintained. The difficulties encountered in the x value determination from normal transmission curves, i.e., from E0(x), due to the Burstein–Moss shift are discussed. In order to overcome these difficulties, the x values of the Hg1−xCdxTe epilayers were also determined from E1(x). A calibration of E1(x) resulted in small but significant discrepancies with the literature. Extrinsic As doping using the δ doping technique is demonstrated and a very high atomic sheet density of 1.2×1013 cm−2 is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352979
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  • 8
    Electronic Resource
    Electronic Resource
    A new model for the absorption coefficient of narrow-gap (Hg,Cd)Te that simultaneously considers band tails and band filling (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3486-3492 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A semiempirical model is presented that correlates the broadening of the absorption edge with both transitions below the energy gap and with transitions by the Kane band model. This model correctly fits both the absorption and luminescence spectra of narrow-gap (Hg,Cd)Te samples that have been grown by the traveling heater method as well as by molecular-beam epitaxy. The accuracy of the band-gap determination is enhanced by this model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352954
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  • 9
    Electronic Resource
    Electronic Resource
    Oxygen on the (100) CdTe surface (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7385-7388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated oxygen on CdTe substrates by means of x-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). A Te oxide layer that was at least 15 A(ring) thick was found on the surface of as-delivered CdTe substrates that were mechanically polished. This oxide is not easily evaporated at temperatures lower than 350 °C. Furthermore, heating in air, which further oxidizes the CdTe layer, should be avoided. Etching with HCl acid (15% HCl) for at least 20 s and then rinsing with de-ionized water reduces the Te oxide layer on the surface down to 4% of a monoatomic layer. However, according to XPS measurements of the O 1s peak, 20%–30% of a monoatomic layer of oxygen remains on the surface, which can be eliminated by heating at temperatures ranging between 300 and 340 °C. The RHEED patterns for a molecular beam epitaxially (MBE)-grown CdTe film on a (100) CdTe substrate with approximately one monoatomic layer of oxidized Te on the surface lose the characteristics of the normal RHEED patterns for a MBE-grown CdTe film on an oxygen-free CdTe substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354096
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of laser illumination and high energy electrons on molecular-beam epitaxial growth of CdTe (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 268-272 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a detailed investigation on the Te-stabilized (2×1) and the Cd-stabilized c(2×2) surfaces of (100) CdTe substrates. The investigation demonstrates for the first time that both laser illumination and, to a greater extent, high-energy electron irradiation increase the Te desorption and reduce the Cd desorption from (100) CdTe surfaces. Thus it is possible by choosing the proper growth temperature and photon or electron fluxes to change the surface reconstruction from the normally Te-stabilized to a Cd-stabilized phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347706
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