B. A. Andreev

Silicon as an advanced window material for high power gyrotrons

The absorptivity of high-purity grades of silicon (Si) and its reduction by subsequent doping procedures are investigated.The dielectric data are given for the wide range of frequencies (30 – 330 GHz) and temperatures (30 – 330 K) in comparison with the data set for sapphire. The advanced material performance in high power window applications is discussed taking into account both dielectric properties of the optimized silicon grades and thermal conductivity.

Oxygen aggregation in Czochralski-grown silicon heat treated at 450 °C under compressive stress

It has been established that the oxygen aggregation processes in Czochralski-grown silicon (Cz–Si) at 450 °C are strongly affected by high hydrostatic pressure. We observed the enhanced production of shallow thermal donors with ionization energies of 30–40 meV and deep donors at ≈EC−0.1 eV under a pressure of 1 GPa. In contrast, the concentration of the well-known double thermal donors was found to be much less than that in Cz–Si heat treated without stress. The latter effect may be associated with the involvement of self-interstitials in their formation. The enhanced production of other thermal donors is thought to be caused by increasing diffusivity of oxygen under the high stress.

GaAsSb/GaAs strained structures with quantum wells for lasers with emission wavelength near 1.3 μm

Optimum conditions for the growth of the GaAs1 − xSbx/GaAs heterostructures by the method of molecular-bean epitaxy are determined; it is shown that effective long-wavelength photoluminescence at T = 300 K can be obtained at wavelengths as long as λ = 1.3 μm by increasing the antimony incorporation. As the excitation power is increased, the appearance of a short-wavelength line (in addition to a shift of a photoluminescence maximum to shorter wavelengths characteristic of the type II heterojunctions) related to direct optical transitions in the real space takes place; this relation is confirmed by the results of studying the photoluminescence spectra with subpicosecond and nanosecond time resolution in the case of pulsed excitation.

Strain-driven alloying: effect on sizes, shape and photoluminescence of GeSi/Si(001) self-assembled islands

The effect of strain-driven alloying on sizes, shape and the photoluminescence (PL) properties of Ge(Si)/Si(001) self-assembled islands was investigated for temperatures of Ge deposition above 550 °C using atomic force microscopy (AFM), X-ray analysis, Raman spectroscopy. We found out that strain-driven Si diffusion into Ge/Si(001) self-assembled islands causes formation of an alloy in islands at these growth temperatures. An increase in the Ge content in the islands with a lower growth temperature results in a decrease of the pyramid-islands volume at which they transform to dome-islands. The energy of the optical transition in the free-standing islands was calculated using the observed values of the islands composition and elastic strain. The discrepancy between the calculated energy and the data observed from photoluminescence spectra is related to the changes of composition and height of the islands during Si overgrowth.

Lanthanide complexes with substituted naphtholate ligands: extraordinary bright near-infrared luminescence of ytterbium

A series of Pr, Nd, Ho, Er, Tm, and Yb complexes with 3-(2-benzoxazol-2-yl)-2-naphtholate and 3-(2-benzothiazol-2-yl)-2-naphtholate ligands was synthesized. The structure, as well as the photo- and electroluminescent properties of these complexes were studied. An extraordinary bright emission of Yb3+ was detected. To explain the phenomenon, a novel excitation mechanism involving intramolecular electron transfer was proposed.

Infrared lateral photoconductivity of InGaAs quantum dot heterostructures grown by MOCVD

Abstract InGaAs/GaAs quantum dots (QD) multilayer modulation-doped structures for infrared photodetector application were grown by the low-pressure metalorganic chemical vapor deposition. Normally incidence photoconductivity (PC) with a lateral electron transport was observed in samples, when the In supply during the QD formation was varied. At low temperature (near 4 K ) PC peak was observed near 16 μm . With increasing temperature another PC peak appeared near 5 μm .

Er3+ photoluminescence excitation spectra in erbium-doped epitaxial silicon structures

Excitation spectra of erbium photoluminescence (λ=1540 nm) in Si: Er epitaxial structures were studied within a broad pump wavelength range (λ=780–1500 nm). Erbium photoluminescence was observed to occur at pump energies substantially less than the silicon band-gap width. Possible mechanisms of erbium ion excitation in this pump radiation energy region are discussed.

Er-Doped Electro-Optical Memory Element for 1.5-

Silicon photonics is rapidly growing and a number of Si-based active and passive components have recently been demonstrated. We demonstrate new functionality of Er-doped silicon: a memory effect in electroluminescence. This finding opens a prospect of necessary, and thus far not available, component for Si optoelectronics-a fully complimentary metal-oxide-semiconductor-compatible electro-optical converter with a memory function, operating in the technologically important 1.5-mum band. When developed and optimized, prospect applications could include optical intraand inter-chip connectors and volatile flash memory elements

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The IR spectra of all three Si isotopes in the form of bulk single crystals (28Si with an enrichment of more than 99.9%, and 29Si and 30Si with an enrichment of more than 90%) have been studied at T = 300, 17, and 5 K in the spectral range 550–1200 cm−1. The IR active local vibrational modes (LVM) of Si-12C centered at 605 cm−1 and Si-16O-Si quasi-molecules in the region of 1136 cm−1 for all the Si isotopes, in comparison with Si possessing a natural isotopic composition, as well as their isotopic shift at 300 and 17 K, have been determined. The dependence of the shape of the antisymmetric stretching vibration band for 28Si-16O-28Si in the spectrum of 28Si on spectral resolution has been studied. The possibility of generalizing the IR spectroscopy method for the determination of carbon and oxygen impurities in Si possessing a natural isotopic composition to monoisotopic Si have been discussed.

m Silicon Photonics

Energy transfer to free carriers in an Auger process is well known to hamper emission of rare-earth dopants in semiconductors. In particular, this process limits the excitation mechanism and is partly responsible for the thermal quenching of the ~1.5 µm photoluminescence from Er3+ ions embedded in the crystalline silicon matrix. In this contribution, we investigate the excitation cross section and the free-carrier Auger process in Er-doped silicon multinanolayer structures. This novel Si-based material has recently been shown to exhibit very interesting properties as regards photonic applications.