Impact excitation of Er-doped GaAs and the rare-earth sites in III-V compound semiconductors

1993 ◽  
Vol 301 ◽  
Author(s):  
S. J. Chang ◽  
K. Takahei ◽  
J. Nakata ◽  
Y. K. Su
Keyword(s):  
Energy Transfer ◽  
Interstitial Site ◽  
Impact Excitation ◽  
Electron Hole ◽  
Pl Spectra ◽  
Gaas Substrates ◽  
Tetrahedral Interstitial Site ◽  
Different Temperatures ◽  
Er Doped ◽  
Hole Recombination

ABSTRACTWe report the first study of impact excitation of Er ions in GaAs. The MOCVDgrown, p+-n structured EL devices were fabricated by growing, at different temperatures, GaAs:Er layers on top of the n+ GaAs substrates. P+ layers were made by Zn diffusion from the top surfaces. When we forward biased these diodes, their EL spectra were similar to their respective PL spectra for each sample but different from each other's. However, when we reverse biased these diodes, EL spectra obtained from all samples are the same, which were different from their PL spectra. These results indicate that the Er center(s) excited by direct impact is different from the Er center(s) excited through electron-hole recombination and subsequent energy transfer. By using RBS channeling, we found that most of the Er ions, in our MOCVD-grown GaAs:Er samples, occupy a displaced tetrahedral interstitial site. From these PL, EL and RBS results, we conclude that only a small amount of Er ions emit luminescence when they are indirectly excited through energy transfer.

Detection of directed electron-hole recombination energy transfer from an ionic crystal matrix to self-assembled nanocrystals

JETP Letters ◽  
2005 ◽  
Vol 82 (11) ◽  
pp. 727-730 ◽  
Author(s):  
P. G. Baranov ◽  
N. G. Romanov ◽  
A. G. Badalyan ◽  
D. O. Tolmachev ◽  
V. L. Preobrazhenskii
Keyword(s):  
Energy Transfer ◽  
Ionic Crystal ◽  
Recombination Energy ◽  
Electron Hole ◽  
Crystal Matrix ◽  
Self Assembled ◽  
Hole Recombination

Lattice Location and Photoluminescence of Er in GaAs and Al0.5Ga0.5As

1993 ◽  
Vol 301 ◽  
Author(s):  
E. Alves ◽  
M.F. Da Silva ◽  
A. A. Melo ◽  
J.C. Soares ◽  
G.N. Van Den Hoven ◽  
...  
Keyword(s):  
Room Temperature ◽  
Interstitial Site ◽  
Lattice Location ◽  
Temperature Correlation ◽  
Gaas Substrates ◽  
Trivalent State ◽  
Er Doped

ABSTRACTEpitaxial Er-doped GaAs and Al0.5Ga0.5As films, 1.6 μm thick, grown by MBE on (100) GaAs substrates at 560°C, with Er concentrations in the range 9 × 1017 to 2 × 1020 cm−3 were studied with RBS/channeling and photoluminescence techniques. Angular scans in the <110> and <111> axial and (111) planar directions indicate that the Er atoms in GaAs are located on interstitial sites. In Al0.5Ga0.5As doped with 5 × 1019 Er cm−3, 70% of the Er atoms are on positions slightly displaced from the interstitial site, the rest presumably substitutional. In Al0.5Ga0.5As doped with 9 × 19 Er cm−3, more than 88% of the Er atoms are on substitutional sites.Photoluminescence around 1.54 μm is observed at room-temperature in Er-doped Al0.5Ga0.5As. Both the low and highly Er-doped samples show similar luminescence intensities; the luminescence lifetimes are on the order of 1 ms. The Er-doped GaAs does not show any measurable signal at room-temperature. Correlation of the luminescence data to the Er lattice location suggests that only substitutional Er in AlGaAs is in the luminescent trivalent state.

Multiple Helium Atoms Diffusion in Tungsten: A Molecular Dynamic Simulation

2014 ◽  
Vol 789 ◽  
pp. 549-553
Author(s):  
Peng Tao ◽  
Xiao Lin Shu
Keyword(s):  
Bond Order ◽  
Arrhenius Equation ◽  
Interstitial Site ◽  
Diffusion Barriers ◽  
Helium Atoms ◽  
Tetrahedral Interstitial Site ◽  
Mean Squared Displacement ◽  
Different Temperatures ◽  
Bond Order Potential ◽  
The Mean

The diffusion process of multiple He atoms in W is simulated by a molecular dynamics (MD) method with the W-H-He analytic bond-order potential. The diffusivities of different number of helium (He) atoms in W are determined by the mean squared displacement (MSD) method at different temperatures. The diffusivity-temperature (D-T) relationship is fitted to the Arrhenius equation to obtain the pre-factor and the diffusion barrier. Under the temperature of 1200K He atoms diffuse together, and above 1200K they separate from each other. When the number of He atoms is greater than three, all He atoms oscillate at the tetrahedral interstitial site (TIS) instead of diffusing under 400K. In the temperature range of 400-1200K, the diffusion barriers of He atoms, the number of which is from two to five, are 0.098, 0.170, 0.125 and 0.112eV, respectively. Contrasting with one He atom (0.058eV), the higher diffusion barriers reflect a greater difficulty in diffusion of multiple He atoms in W. In addition, when the number of He atoms is over five, vacancies are formed in W, and He atoms occupy the vacancies.

Exciton photoluminescence and energy transfer in nanocrystalline Si/ Si dioxide superlattice structures

2003 ◽  
Vol 789 ◽  
Author(s):  
V. Yu. Timoshenko ◽  
O. A. Shalygina ◽  
M. G. Lisachenko ◽  
P. K. Kashkarov ◽  
D. Kovalev ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Strong Emission ◽  
Thermal Crystallization ◽  
Different Temperatures ◽  
Amorphous Si ◽  
Superlattice Structures ◽  
Er Doped ◽  
Excitation Conditions ◽  
Excitonic Recombination ◽  
Nanocrystalline Si

ABSTRACTPhotoluminescence (PL) of nanocrystalline Si (nc-Si) assemblies formed by thermal crystallization of amorphous Si/SiO2 and SiO/SiO2 superlattices (SLs) has been investigated at different temperatures and excitation conditions. The low temperature resonant PL spectroscopy reveals phonon-assisted excitonic recombination. At room temperature the samples formed from a-SiO/SiO2 SLs possess relatively high PL quantum yield (∼ 1%). The PL transients have non-exponential decay, which indicates the exciton energy transfer in nc-Si ensembles. The excitonic energy of Er-doped nc-Si SL structures can be almost completely transferred to Er ions incorporated in SiO2 matrix that results in a strong emission line at 0.81 eV.

Excitation Mechanisms and Light Emitting Device Performances in Er-Doped Crystalline Si

1996 ◽  
Vol 422 ◽  
Author(s):  
F. Priolo ◽  
S. Coffa ◽  
G. Franzo ◽  
A. Polman
Keyword(s):  
Reverse Bias ◽  
Crystalline Silicon ◽  
Forward Bias ◽  
Depletion Region ◽  
Impact Excitation ◽  
Electron Hole ◽  
Light Emitting ◽  
Temperature Operating ◽  
Excitation Mechanisms ◽  
Er Doped

AbstractIn this paper the performances of room temperature operating light emitting diodes (LEDs), fabricated by Er ion implantation of crystalline silicon, are investigated in detail. It is shown that 1.54 μm emission is observed under both forward and reverse bias operation, with a much higher intensity under reverse bias. The excitation mechanisms of Er3+ are demonstrated to be very different in the two cases: under forward bias Er is excited through the electron - hole recombination at an Er - related level, while under reverse bias impact excitation by hot carriers represents the excitation process. This last mechanism is shown to occur with a cross section of 6 × 10−17 cm2 and population inversion of the excitable Er sites within the depletion region is demonstrated. The efficiency and limitations of this approach are also discussed.

Electroluminescent Devices Made from Silicon Nanocrystals Embedded in Various Host Matrices

1996 ◽  
Vol 452 ◽  
Author(s):  
Gildardo R. Delgado ◽  
Howard W. H. Lee ◽  
Khashayar Pakbaz
Keyword(s):  
Silicon Nanocrystals ◽  
Impact Excitation ◽  
Optical And Electrical Properties ◽  
Carrier Injection ◽  
Electron Hole ◽  
Electroluminescent Devices ◽  
Advantages And Disadvantages ◽  
Si Nanocrystals ◽  
Host Matrices ◽  
Hole Recombination

AbstractSi nanocrystals produced by ultrasonic fracturing of porous silicon (PSi) were used to fabricate electroluminescent (EL) devices. The active EL material consists of Si nanocrystals embedded in various host matrices such as polyvinylcarbazole (PVK), polymethylmethacrylate (PMMA), and silica sol-gels. Several device configurations were used to induce EL processes that rely on radiative electron-hole recombination via carrier injection or impact excitation of the nanocrystals. We report on the optical and electrical properties of these devices. We discuss relevant physics pertaining to the Si nanocrystals/host and discuss advantages and disadvantages among the different host matrices.

Optically Detected Magnetic Resonance and Double Beam Photoluminescence of CdS/HgS/CdS Nanoparticles

1998 ◽  
Vol 536 ◽  
Author(s):  
H. Porteanu ◽  
A. Glozman ◽  
E. Lifshitz ◽  
A. Eychmüller ◽  
H. Weller
Keyword(s):  
Optical Properties ◽  
Magnetic Resonance ◽  
Cds Nanoparticles ◽  
Electron Hole ◽  
Cladding Layer ◽  
Double Beam ◽  
Optically Detected Magnetic Resonance ◽  
Optically Detected ◽  
Cladding Layers ◽  
Hole Recombination

AbstractCdS/HgS/CdS nanoparticles consist of a CdS core, epitaxially covered by one or two monolayers of HgS and additional cladding layers of CdS. The present paper describes our efforts to identify the influence of CdS/HgS/CdS interfaces on the localization of the photogenerated carriers deduced from the magneto-optical properties of the materials. These were investigated by the utilization of optically detected magnetic resonance (ODMR) and double-beam photoluminescence spectroscopy. A photoluminescence (PL) spectrum of the studied material, consists of a dominant exciton located at the HgS layer, and additional non-excitonic band, presumably corresponding to the recombination of trapped carriers at the interface. The latter band can be attenuated using an additional red excitation. The ODMR measurements show the existence of two kinds of electron-hole recombination. These electron-hole pairs maybe trapped either at a twin packing of a CdS/HgS interface, or at an edge dislocation of an epitaxial HgS or a CdS cladding layer.

Pre-Industrial Experience in Solar Photocatalytic Mineralization of Real Wastewaters. Application to Pesticide Container Recycling

1999 ◽  
Vol 40 (4-5) ◽  
pp. 123-130 ◽  
Author(s):  
S. Malato ◽  
J. Blanco ◽  
C. Richter ◽  
B. Milow ◽  
M. I. Maldonado
Keyword(s):  
Organic Contaminants ◽  
Toxic Waste ◽  
Experimental Plant ◽  
Electron Hole ◽  
Particulate Suspensions ◽  
Photocatalytic System ◽  
Commercial Pesticide ◽  
Pesticide Container ◽  
By Products ◽  
Hole Recombination

Particulate suspensions of TiO2 irradiated with natural solar tight in a large experimental plant catalyse the oxidation of organic contaminants. The problem in using TiO2 as a photocatalyst is electron/hole recombination. One strategy for inhibiting e−/h+ recombination is to add other (irreversible) electron acceptors to the reaction. In many highly toxic waste waters where degradation of organic pollutants is the major concern, the addition of an inorganic anion to enhance the organic degradation rate may be justified. For better results, these additives should fulfil the following criteria: dissociate into harmless by-products and lead to the formation of ·OH or other oxidising agents. In this paper, we attempt to demonstrate the optimum conditions for the treatment of commercial pesticide rinsates found in the wastewater produced by a pesticide container recycling plant. The experiments were performed in one of the pilot plants of the largest solar photocatalytic system in Europe, the Detoxification Plants of the Plataforma Solar de Almería (PSA), in Spain. After testing ten different commercial pesticides, results show that peroxydisulphate enhances the photocatalytic miniralization of all of them. This study is part of an extensive project focused on the design of a solar photocatalytic plant for decontamination of agricultural rinsates in Almería (Spain).

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