Conductivity compensation and deep traps in epitaxial n-GaAs irradiated by electrons

A study has been made of electrophysical properties and deep traps in epitaxial n-GaAs grown by the chloride method and irradiated by electrons in the temperature range (20–500)°C. It is shown that the natural conductivity of GaAs is attained at irradiation temperatures of 20°C due to the introduction of E traps, and for 300°CT_irr500°C of high-temperature P traps, presumably defect clusters.V. D. Kuznetsov Siberian Physicotechnical Institute at the State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 57–60, October, 1992.     

分子束外延n-GaAs/SI-GaAs薄膜材料的拉曼光谱研究

用分子束外延(MBE)技术, 在GaAs(100)衬底上生长了不同Si掺杂浓度（从1016 cm-3到1018 cm-3）的n-GaAs薄膜。通过在室温下拉曼光谱的测量对n-GaAs薄膜的谱形进行了分析,拉曼位移出现了明显的移动,光学横模TO峰相对的增强,光学纵模LO峰相对的减弱。文章分析了原因这是由于Si掺杂浓度不断的提高,致使界面失配位错不断地提高造成的,内部应力也在不断的增大,原来的晶格振动平衡被破坏,四价Si替代了三价Ga致使谱线移动。并且由于横声子模具有Raman活性,横声子模被相对的增强了。实验结果与理论是互相吻合的。     

Broadening of vibration Q-bands in the Raman spectrum of carbon dioxide due to critical density fluctuations

Detailed analysis of CARS-spectroscopy experimental data of the carbon dioxide Fermi dyad showed that critical density variance should not exceed 0.1 and the lifetime of critical fluctuations is more than 10 ns. To interpret the experimental data, an original calculation of the critical fluctuation contribution to spectral line, considering the lifetime of critical fluctuations, was performed.     

Electron spectrum and intrinsic absorption of heavily doped n-GaAs

The article presents results of a numerical calculation, made with a computer, of several parameters and functions characterizing the electron spectrum of heavily doped semiconductors; in addition, the article presents theoretically calculated and experimentally obtained dispersion curves of the absorption coefficient in the region of interband transitions in heavily doped n-GaAs. The numerical calculation method is based upon the work of V. L. Bonch-Bruevich, who used Green functions. Calculations and experimental measurements were made for n-GaAs with free electron concentrations of 4.8·10¹⁸ cm^?3 at temperatures of 10–610?K. Agreement between the theoretically calculated and the experimentally obtained values of the absorption coefficient is observed in the edge region at photon energies exceeding the width of the forbidden band of the pure semiconductor.     

Resonance enhancement of Raman scattering by electron-gas excitations of n-GaAs

Large resonance enhancements in the inelastic light scattering intensities involving free carriers have been measured at the E₀ + Δ₀ energy gap of n-GaAs.Results for spin-flip single particle excitations are well described as unscreened intraband scattering involving the Γ₇ valence band as intermediate state. The resonance of the longitudinal plasmon-phonon coupled modes indicates the contribution of other so far not fully identified processes.     

Raman scattering in a near-surface n-GaAs layer implanted with boron ions

Structure in the Raman scattering spectra of near-surface n-GaAs layers (n=2×10¹⁸ cm⁻³) implanted with 100 keV B⁺ ions in the dose range 3.1×10¹¹–1.2×10¹⁴ cm⁻² is investigated. The qualitative and quantitative data on the carrier density and mobility and on the degree of amorphization of the crystal lattice and the parameters of the nanocrystalline phase as a result of ion implantation are obtained using a method proposed for analyzing room-temperature Raman spectra. Fiz. Tverd. Tela (St. Petersburg) 41, 1495–1498 (August 1999)     

Spin fluctuations of nonequilibrium electrons and excitons in semiconductors

Effects that are related to deviations from thermodynamic equilibrium have a special place in modern physics. Among these, nonequilibrium phenomena in quantum systems attract the highest interest. The experimental technique of spin-noise spectroscopy has became quite widespread, which makes it possible to observe spin fluctuations of charge carriers in semiconductors under both equilibrium and nonequilibrium conditions. This calls for the development of a theory of spin fluctuations of electrons and electron–hole complexes for nonequilibrium conditions. In this paper, we consider a range of physical situations where a deviation from equilibrium becomes pronounced in the spin noise. A general method for the calculation of electron and exciton spin fluctuations in a nonequilibrium state is proposed. A short review of the theoretical and experimental results in this area is given.     

Energy spectrum of ejected electrons in ionization of hydrogen atoms by electrons

Energy spectrum of ejected electrons in ionization of hydrogen atoms has been calculated following a multiple scattering theory of Das and Seal [15]. The results show peaks around two to three Rydbergs of energies of the ejected electrons, for incident electron energy of 250 eV and 500 eV, considered here, and for different combinations of the angular variables of the scattered and the ejected electrons, for scattering in a plane. The peaks are very similar to those observed in relativistic K-shell ionization of Ag atoms by electrons at 500 KeV energy [6]. The physical origin of these peaks may be traced to the second order scatterings, scattering first by the atomic nucleus (or the atomic electron) and then a second time by the atomic electron. These peaks are, however, absent in the first Born results. Experimental verification of the present results and theoretical calculation by some other well-known methods will be interesting.     

Raman spectrum of monobromoindigo

Monobromoindigo is a component of Tyrian purple, a purple–red natural colorant extracted from various species of sea snails, which was possibly first produced by the ancient Phoenicians and has been employed as a symbol of royalty and power by several civilizations over the centuries. Raman spectroscopy has proved to be an effective analytical technique to detect historical dyes, as it allows rapid and accurate identification of unknowns in a nondestructive way. Although other constituents of Tyrian purple have been comprehensively investigated by Raman spectroscopy, the Raman bands of 6‐bromoindigo, a molecule that has been correlated with a specific snail species, Hexaplex trunculus (also known as Murex trunculus), have been reported but not previously assigned. This paper includes a complete assignment of the Raman spectrum of the 6‐bromoindigo isomer, including experimental spectra recorded at 488 and 785 nm, which were compared with those collected from indigo under the same conditions. 1 1 This article was first published online 03 November 2011. Errors were subsequently identified. This notice is included in both print and online versions to indicate that both have been corrected 07 December 2011.
Theoretical Raman spectra for both molecules were obtained using density functional theory calculations. Copyright © 2011 John Wiley & Sons, Ltd.     

The energy spectrum of electrons in a crystal

The principal theorems concerning these characters are presented.     

Raman scattering from antiferromagnetic spin fluctuations

A microscopic theory for the scattering of light from spin fluctuation pair modes in the two-dimensional Hubbard model is presented. Two-spin fluctuation processes with opposite momenta near the antiferromagnetic wave vectorQ=(, ) are shown to contribute in particular to the low energy part of the Raman cross section. We explicitly investigate the influence of the Raman vertex function that describes the coupling of the Raman vertex function that describes the coupling of the light to the electrons and distinguishes between the different scattering geometries. In addition we explore the dependence on the correlation strength and on the temperature.     

Coulomb fluctuations and Raman scattering in solid electrolytes

The theory of Raman scattering (RS) by superionic conductors (SC) is presented. It is shown that the RS central peak in SC of the α-AgI type is caused by two-mode relaxation processes. The phonon shoulder is due to the first-order scattering on the optical phonon mode and is chiefly determined by the screening effects in SC. Proposed theory gives explanation of the RS experiments which had not been interpreted consistently so far.