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1

Free Carrier Scattering in Metallic n-GaAs in the Presence of Static Lattice Distortions Due to a Partial Chemical Order of Impurities

100%

Słupiński T., Molas M., Papierska J.

Acta Physica Polonica A

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2009

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vol. 116

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issue 5

979-982

EN

Simple electric transport versus T = 20-400 K in metallic n-GaAs annealed single crystals with Te impurity concentration ∿(0.4-1.7) × 10^{19} cm^{-3}, which is above the equilibrium doping limit, is reported and compared with modern theory of electron mobility in degenerated n-GaAs by Szmyd, Hanna, Majerfeld. An overcome of the equilibrium doping limit in annealed n-GaAs is manifested by a lowered electrical activation of Te donors and by an onset of ≈ 0.1-1 μm regions of local strain in the crystal lattice known from high resolution X-ray studies. These preliminary results of transport show that the electron mobility μ(T) measured for n-GaAs with local strains is not consistent with predictions of Szmyd et al. model for any degree of compensation assumed. This surprising result indicates that electric transport in materials above the equilibrium doping limit is not well understood assuming the scattering by ionized impurities. The nature of defects responsible for an observed strong reduction of free carrier concentration (here ≈ 80%) in annealed heavily doped n-GaAs seems not to be related with electrical compensation. We point here at the possible role of effects of free carrier scattering due to static lattice distortions (local strains) related to a chemical aggregation of impurity atoms. We also notice that transport in metallic n-GaAs with local strains shows features similar to a weak localization σ_{xx} ∝ log T.

2

Structural, Morphological and Optical Study of Bismuth and Zinc Co-Doped Yttrium Oxide Prepared by Solvothermal and Wet Chemical Method

100%

Bhavani G., Ganesan S.

Acta Physica Polonica A

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2016

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vol. 130

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issue 6

1373-1379

EN

Yttrium oxide (Y₂O₃) is the most familiar yttrium compound, which is popularly known as host for ion doping of other rare earth elements. Bismuth ion (Bi³⁺) is well known as an activator and sensitizer in several particular phosphors. Zinc oxide (ZnO) nanomaterial, having a wide band gap, is one of the promising candidates for general illumination applications due to its high optical transparency and color tenability bismuth (Bi) and zinc (Zn) co-doped Y₂O₃ samples are synthesized by simple precipitation techniques like solvothermal and wet chemical methods. The prepared samples were characterized using X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectra, ultraviolet-visible absorbance spectroscopy and photoluminescence spectrophotometry. Ultraviolet-visible absorption studies showed absorption only around 340 nm whereas photoluminescence shows peaks around 500 nm, 680 nm, and 1020 nm for Bi and Zn co-doped Y₂O₃. The photoluminescence spectrum shows emission in blue region (500 nm) due to Zn dopant and red and near infrared region (680 and 1020 nm) due to Bi dopant. This is a new material which can effectively work as an efficient and cheap red phosphor.

3

Optical Absorption and Luminescence of Gd_{3}Ga_{5}O_{12}:Cr,Mg Epitaxial Films

100%

Zakharko Y., Syvorotka I., Luchechko A., Syvorotka I., Sugak D., Vakiv M.

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issue 1

111-113

EN

The optical absorption, emission spectra and luminescence decay kinetics under photoexcitation of Gd_{3}Ga_{5}O_{12} (GGG) garnet epitaxial films doped with Cr^{3+} ions and co-doped with Cr^{3+} and Mg^{2+} ions have been investigated. Luminescence of the GGG:Cr films due to ^{4}T_{2} → ^{4}A_{2} and ^{2}E → ^{4}A_{2} transitions in Cr^{3+} ions have been observed. Increase of the activator ions concentration has an influence on the intensity and decay time of Cr^{3+} ions photoluminescence. Introduction of the magnesium ions leads to partial transformation of chromium valence state (Cr^{3+} → Cr^{4+}) and to the appearance of a broad absorption band with the maximum at 860 nm. The narrow lines with luminescence maxima at 704 and 706 nm have arisen in the highly doped GGG:Cr,Mg films.

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3 Acta Physica Polonica A

1 2016

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1 Bhavani G.

1 Ganesan S.

1 Luchechko A.

1 Molas M.

1 Papierska J.

1 Sugak D.

1 Syvorotka I.

1 Słupiński T.

1 Vakiv M.

1 Zakharko Y.

Free Carrier Scattering in Metallic n-GaAs in the Presence of Static Lattice Distortions Due to a Partial Chemical Order of Impurities

Structural, Morphological and Optical Study of Bismuth and Zinc Co-Doped Yttrium Oxide Prepared by Solvothermal and Wet Chemical Method

Optical Absorption and Luminescence of Gd_{3}Ga_{5}O_{12}:Cr,Mg Epitaxial Films