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Excitation Density (excitation + density)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Cathodoluminescence studies of large bulk AlN crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003
E. Silveira
Abstract The optical properties of high quality large bulk AlN crystals have been tested by cathodoluminescence measurements carried out at different temperatures, excitation densities and electron beam energies. Both c -plane (0001) and a -plane () wafers were cut from bulk, single-crystals of AlN which were fabricated by the sublimation-recondensation technique. The wafer surfaces were subsequently prepared by chemical-mechanical polishing. The low-temperature near-band-edge cathodoluminescence spectra of a typical a-plane oriented AlN crystal show up to five transitions, which are tentatively assigned to free- and bound exciton recombination processes. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Manifestation of the equilibrium hole distribution in photoluminescence of n-InN

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2005
A. A. Klochikhin
Abstract Photoluminescence (PL) of n-InN grown by molecular beam epitaxy with Hall concentrations from 3.6 to 7.3 × 1017 cm,3 demonstrates dependences on carrier concentration, temperature, and excitation density which give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The structure of the PL spectra observed at 4.2 and 77 K in the energy interval from 0.50 to 0.67 eV indicates that a considerable part of holes is trapped by deep and shallow acceptors before the interband recombi- nation with degenerate electrons occurs. At room temperature, the band-to-band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by model calculations under the assumptions of a band gap equal to 0.665,0.670 eV at zero temperature and zero carrier concentration and a non-parabolic conduction band with the effective mass at the G -point equal to 0.07 of the free electron mass. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Fabrication and optical properties of nano-structured semipolar InGaN/GaN quantum wells on c-plane GaN template

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
Hongbo Yu
Abstract High density self-assembled nanostructured semipolar (NSSP) GaN pyramids are fabricated based on c-plane GaN template by in situ silane treatment followed by high temperature treatment. Semipolar InGaN/GaN multiple quantum wells (MQWs) were subsequently grown on the NSSP GaN. Optical properties of the MQWs were studied by temperature- dependent and excitation density varied photoluminescence. It was found that the internal electric field in the NSSP MQWs were remarkably reduced in comparison with planar c-plane MQWs. The internal quantum efficiency of the NSSP MQWs was measured to be > 30% which showed potential applications in III-nitride light emitters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dependence of long-lived defect creation on excitation density in MgO single crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
Aleksandr Lushchik
Abstract The processes of the creation, stabilization and annealing of anion Frenkel defects have been investigated in MgO and MgO:Be single crystals irradiated by , particles, uranium swift ions or fast neutrons at 300 K and also additionally irradiated by 5 keV electrons at 6 K. Neutral oxygen interstitials undergo stabilization due to their association with the holes localized near Be2+ ions or near cation vacancies. The peculiarities of the processes of nonimpact creation and stabilization of point defects under conditions of a high density of electronic excitations formed in the tracks of swift heavy ions have been considered by the example of MgO crystals, where the creation energy of a pair of long-lived Frenkel defects exceeds the energy gap, EFD > Eg. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Quantum beats between magnetic field split states in semiconductor microcavity

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2005
M. N. Makhonin
Abstract Spin properties of quantum well excitons in the active layer of planar micricavity have been analyzed using pump-and-probe technique in magnetic fields normal to the cavity plane. When exciting the cavity polaritons with linearly polarized ps pulses the differential transmission (DT) spectra show a time oscillation both in the DT signal, IDT, and spectral position of ,+ and ,, polarized lower polariton (LP) states E+ and E,. The oscillation in IDT and E+ - E, is inverse in the magnetic field and shown to be controlled by rotating the LP polarization plane due to the difference in the ,+ and ,, LP energies. The period coincides for IDT and E+ - E, whereas the phase of their oscillation differs from each other by ,/4. The decay of quantum beats increases with excitation density due to an enhanced interparticle scattering. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Microphotoluminescence of strongly localized states in InGaN/GaN layers , emission of quantum dots?

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
Henning Lohmeyer
Abstract We report on microphotoluminescence-spectroscopy results giving strong evidence for the existence of quantum-dot like localization centers (LCs) in InGaN/GaN heterostructures. The observed low surface density of the LCs allows to address individual emitting centers without lateral structuring of the sample. The optical properties of the LCs with respect to the dependence on excitation density and temperature are studied. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Influence of excitation density on luminescence decay in Y3Al5O12:Ce and BaF2 crystals excited by free electron laser radiation in VUV

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005
M. Kirm
Abstract The influence of excitation density on luminescence decay in Y3Al5O12:Ce and BaF2 crystals at room temperature was investigated for the first time using pulsed free electron laser radiation in vacuum ultraviolet. Increased excitation density led to the remarkable shortening of luminescence decays with non-exponential behaviour in both crystals. The possible reasons for dramatic changes in the dynamics of electronic excitations in insulators excited by free electron laser radiation will be discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Conversion of an electron,hole plasma into a high density excitonic state in ZnO epitaxial thin films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004
Y. Toshine
Abstract Time-resolved luminescence spectra of an exciton-exciton scattering process and an electron,hole plasma (EHP) were measured in ZnO epitaxial thin films by the optical Kerr gate method. At moderate excitation density below critical Mott density, stimulated emission of luminescence due to the exciton,exciton scattering process (P band) was observed. The P band shows a red shift and spectral narrowing in the first 1,2 ps after the excitation which reflects a thermal redistribution of excitons in the n = 1 excitonic state. On the other hand, at high excitation density above the critical Mott density, stimulated emission of the luminescence due to the EHP was observed. After thermalization of the EHP, the luminescence intensity of the EHP band decreases with time, and the EHP band converts to the P band after ,10 ps through a reverse Mott transition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]