Polycrystalline thin film ZnSexTe1-x: preparation and properties
TL;DR: ZnSexTe1-x films were prepared by co-evaporating ZnSe and ZnTe powders from a two-zone hot wall evaporation jig onto glass substrates.
Abstract: ZnSexTe1-x films were prepared by co-evaporating ZnSe and ZnTe powders from a two-zone hot wall evaporation jig onto glass substrates. The optical band gaps for different x were determined and this showed a bowing behaviour. The refractive indices and extinction coefficients have been determined as a function of wavelength. Variations of surface roughness with composition and microstructural details were also reported. Grain boundary scattering effects were found to be a dominant factor controlling electron transport processes in these films.
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16 Oct 1995
TL;DR: In this paper, the luminescence properties of ZnxMg1-xSe layers were obtained by thermal diffusion of Mg metal in the temperature range 1050 K - 1200 K into ZnSe single crystal grown by Bridgman method, and epitaxial growth on (001) GaAs and (111) ZnTe substrates by MBE using elemental Zn, Se and Mg sources.
Abstract: This work deals with the study of luminescence properties of ZnxMg1-xSe layers prepared by different methods. ZnxMg1-xSe mixed crystal layers were obtained by: (a) thermal diffusion of Mg metal in the temperature range 1050 K - 1200 K into ZnSe single crystal grown by Bridgman method, and (b) epitaxial growth on (001) GaAs and (111) ZnTe substrates by MBE using elemental Zn, Se and Mg sources. The luminescence spectra of ZnxMg1-xSe layers grown on (001) GaAs and (111) ZnTe substrates are dominated by narrow blue and violet emission bands with maxima positioned at about 3.05 - 3.28 eV, 2.88 - 3.04 eV, and 2.81 - 2.705 eV.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Cites background from "Polycrystalline thin film ZnSexTe1-..."
...3) for ZnMg1_Se layers obtained by thermal diffusion of Mg into ZnSe crystal at temperatures: 1200 K curve (1) and 1120 K curve (2), respectively....
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...4 shows the temperature dependence of the intensities of the highest photon energy lines for ZnMg1 _Se layers obtained by thermal diffusion of Mg into ZnSe crystal at temperatures: 1200 K curve (1) and 1120 K curve (2), respectively....
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TL;DR: In this article, Boron doses of 1×1012-5×1015/cm2 were implanted at 60 keV into 1-μm-thick polysilicon films and Hall and resistivity measurements were made over a temperature range −50-250 °C.
Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...
2,657 citations
TL;DR: In this article, the transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain-boundary trapping model, based on the assumption of both a δ-shaped and a uniform energy distribution of interface states.
Abstract: The transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain‐boundary trapping model. The theory has been developed on the assumption of both a δ‐shaped and a uniform energy distribution of interface states. A comparison with experiments indicates that the interface states are nearly monovalent and peaked at midgap. Their density is 3.8×1012 cm−2, in accordance with carrier‐lifetime measurements performed on CVD films.
673 citations
TL;DR: In this paper, a unified theory of exponetial absorption edges must rely on electric microfields as the cause, including exciton effects and the final-state interaction between the electron and the hole, and ascribe Urbach's rule to the relative, internal motion of the exciton.
Abstract: Exponential absorption edges $\ensuremath{\alpha}=A{e}^{g(\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{-}\ensuremath{\hbar}{\ensuremath{\omega}}_{0})}$ have been observed in both ionic (Urbach's rule: $g=\frac{\ensuremath{\sigma}}{{k}_{B}{T}^{*}}$ and covalent materials. Arguments are given to show that a unified theory of exponetial absorption edges must (i) rely on electric microfields as the cause, (ii) include exciton effects and the final-state interaction between the electron and the hole, and (iii) ascribe Urbach's rule to the relative, internal motion of the exciton. An approximate calculation has been made in which the nonuniform microfields are replaced by a statistical distribution of uniform microfields; this calculation is a generalization to physically relevant intermediate-strength fields of previous strong- and weak-field theories of Redfield and Dexter. In contrast with the other microfield models, which obtain the exponential spectral shape by averaging over microfield distributions, the present theory obtains a quantitatively exponential edge as an inherent feature. The temperature dependences of the edges in various materials follow qualitatively from the nature of the microfield sources. The specific temperature dependence of Urbach's rule in ionic crystals is obtained from this model, with supplementary arguments to account for nonuniformity of the fields.
619 citations
TL;DR: In this paper, the optical absorption coefficient for direct, excitonic transitions in a uniform applied electric field is calculated and the electron-hole scattering is treated within the effective mass approximation and leads to an absorption coefficient which differs markedly in size and shape from the Franz-Keldysh absorption spectrum.
Abstract: Numerical calculations of the optical-absorption coefficient for direct, excitonic transitions in a uniform applied electric field are presented. The electron-hole scattering is treated within the effective-mass approximation and leads to an absorption coefficient which differs markedly in size and shape from the Franz-Keldysh absorption spectrum. A detailed numerical study of the shape of the absorption-edge spectrum at photon energies somewhat below the zero-field absorption threshold suggests that for small field strengths the dominant asymptotic form of the absorption coefficient is $\mathrm{exp}(\ensuremath{-}\frac{{C}_{0}|E\ensuremath{-}{{E}_{0}}^{\ensuremath{'}}|}{f})$, where $f=\frac{|e|\mathrm{Fa}}{R}$ is the electric field strength in units of exciton Rydbergs per electron-exciton Bohr radius. This result contradicts the existing belief that the electron-hole interaction does not alter the asymptotic form of the Franz-Keldysh shape: $\mathrm{exp}(\ensuremath{-}\frac{{{C}_{0}}^{\ensuremath{'}}{|E\ensuremath{-}{{E}_{0}}^{\ensuremath{'}}|}^{\frac{3}{2}}}{f})$. Physical arguments are presented to show why the exciton effects should be important. A discussion is presented of the interrelationships among the present treatment of electro-absorption and various one-electron, exciton, and many-body formalisms.
366 citations
TL;DR: In this paper, a new formulation and method are presented for evaluating bandgap, optical transitions and optical constants from the reflectance data for films deposited onto a non-absorbing substrate, which can be used to evaluate the optical properties of the films.
241 citations