1,357,337 research outputs found
Epitaxial growth of GaNAs/GaAs heterostructure materials
No full textA series of systematic experiments on the growth of high quality GaNAs strained layers on GaAs (001) substrate have been carried out by using DC active Nz plasma, assisted molecular beam epitaxy. The samples of GaNAs between 3 and 200 nm thick were evaluated by double crystal X-ray diffraction (XRD) and photoluminescence (PL) measurements. PL and XRD measurements for these samples are in good agreement. Some material growth and structure parameters affecting the properties of GaNAs/GaAs heterostructure were studied; they were: (1) growth temperature of GaNAs epilayer; (2) electrical current of active N-2 plasma; (3) Nz flow rate; (4) GaNAs growth rate; (5) the thickness of GaNAs strained layer. XRD and PL measurements showed that superlattice with distinct satellite peaks up to two orders and quantum well structure with intensity at 22 meV Fourier transform infrared spectroscopy (FWHM) can be achieved in molecular beam epitaxy (MBE) system. (C) 2000 Published by Elsevier Science S.A. All rights reserved
Data for: Non-planarity, scale-dependent roughness and kinematic properties of the Pidima active fault scarp (Messinia, Greece) using high-resolution Terrestrial Lidar data
No full textPoint-cloud dataset from the Pidima active normal fault scarp, Greec
MORPHOTECTONIC ANALYSIS OF THE NEOTECTONIC AND ACTIVE FAULTS OF BEOTIA (CENTRAL GREECE), USING G.I.S. TECHNIQUES
No full textWe study the neotectonic regime and evolution of the central-eastern part of the Asopos River basin (Beotia, Central Greece) which is an area undergoing crustal extension. The main tools that were used in this research were a) field mapping of neotectonic and active normal faults and b) morphotectonic analysis of 59 catchments, which was carried out by GIS techniques. Our results include a) series of maps displaying the spatial variation of morphotectonic indices (sinuosity, asymmetry factor, valley-floor-to-height-ratio etc) and b) map of neotectonic fault segments with associated faultslip data. The morphotectonic analysis indicates that if normal faults in this area are active, they are capable of generating earthquakes with M >6.0
Optical properties and exciton localization in GaNas/GaAs
No full textGaNAs/GaAs single quantum wells (SQWs) and dilute GaNAs bulk grown by molecular beam epitaxy(MBE) were studied by photoluminescence (PL), selectively-excited PL, and time-resolved PL. Exciton localization and delocalization were investigated in detail. Under short pulse laser excitation, the delocalization exciton emission was revealed in GaNAs/GaAs SQWs. It exhibits quite different optical properties from N-related localized states. In dilute GaNAs bulk, a transition of alloy band related recombination was observed by measuring the PL dependence on temperature and excitation intensity and time-resolved PL, as well. This alloy-related transition presents intrinsic optical properties. These results are very important for realizing the abnomal features of III-V-N semiconductors
Exciton Localization and Delocalization in GaNAs/GaAs Quantum Wells
No full textWe have studied exciton localization and delocalization effect in GaNAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy (MBE) using photoluminescence (PL) and timeresolved PL measurements. Studied results suggest that, at low temperature and under a conventional CW excitation, measured PL spectra were dominated by localized exciton (LE) emission caused by potential fluctuations in GaNAs layer. However, under short pulse laser excitation, it is different. An extra high-energy PL peak comes out from GaNAs/GaAs QWs and dominates the PL spectra under high excitation and/or at high temperature. By investigation, we have attributed the new PL peak to the recombination of delocalized excitons in QWs. This recombination process competes with the localized exciton emission, which, we believe, constitutes the "S-shaped" temperature-dependent emission shift often reported in ternary nitrides of InGaN and AlGaN in the literature
Interband luminescence and absorption of GaNAs/GaAs single-quantum-well structures
No full textWe have investigated the interband electron transitions in a GaNAs/GaAs single quantum well (QW) by photoluminescence and absorption spectra. The experimental results show that the dominant photoluminescence at low temperature and high excitation intensity originates from transitions within the GaNAs layer. The interband transition energy for QWs with different well widths can be well fitted if a type-II band line up of GaNAs/GaAs QWs is assumed. (C) 2000 American Institute of Physics. [S0003-6951(00)03220-4]
Effect of SiO2 encapsulation on the nitrogen reorganization in a GaNAs/GaAs single quantum well
No full textEffects of SiO2 encapsulation and rapid thermal annealing on the optical properties of a GaNAs/GaAs single quantum well (SQW) are studied by low-temperature photoluminescence (LTPL). After annealing at 800degreesC for 30s, a blueshift of the LTPL peak energy for the SiO2-capped region is 25meV and that for the bare region is 0.8meV. The results can attribute to the nitrogen reorganization in the GaNAs/GaAs SQW. It is also shown that the nitrogen reorganization can be obviously enhanced by SiO2 cap-layer. A simple model is used to describe the SiO2-enhanced blueshift of the LTPL peak energy. The estimated activation energy of the N atomic reorganization for the samples annealing with and without SiO2 cap-layer are 2.9eV and 3.1eV, respectively
Historical faulting in Aghios Konstantinos area (central Greece), based on archaeological indications
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Optical investigation on the annealing effect and its mechanism of GaInAs/GaNAs quantum wells
No full textThermal annealing of GaInAs/GaNAs quantum wells (QWs) as well as other nitrogen- and indium-contained QW structures grown by molecular beam epitaxy and its effect on optical properties are investigated. The photoluminescence (PL) and photovoltaic (PV) spectra of annealed GaInAs/GaNAs QWs show that the luminescence properties become degraded due to the N diffusion from the GaNAs barrier layers to the GaInAs well layer. Meantime, the annealing-induced blueshift of the PL peak in this QW system is mainly induced by the change of In distribution, suggesting that the In reorganization is greatly assisted by the N-induced defects. The elucidation of annealing effect in GaInAs/GaNAs QW samples is helpful for a better understanding to the annealing effect in the GaInNAs/GaAs QWs. (C) 2003 Elsevier Science B.V. All rights reserved
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