scholarly journals Импульсное лазерное облучение светоизлучающих структур на основе GaAs

2020 ◽  
Vol 54 (12) ◽  
pp. 1336
Author(s):  
О.В. Вихрова ◽  
Ю.А. Данилов ◽  
Б.Н. Звонков ◽  
И.Л. Калентьева ◽  
А.В. Нежданов ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Thermal Effects ◽  
Laser Annealing ◽  
Laser Pulses ◽  
Heat Propagation ◽  
Nonradiative Recombination ◽  
Melting Threshold ◽  
Krf Excimer Laser ◽  
Pulsed Laser Irradiation

The effects of KrF excimer laser pulses on the crystalline and optical properties of structures with four InxGa1−xAs/GaAs quantum wells (x ranged from 0.08 to 0.25) were studied. The results obtained by Raman spectroscopy and reflection spectroscopy showed that the high crystalline quality of the GaAs cap layer is retained after exposure to laser radiation with an energy density of 200 to 360 mJ/cm2. It was established experimentally by photoluminescence spectroscopy and by modeling the laser annealing process, which is a solution to the problem of heat propagation in a one-dimensional GaAs-based system, that the thermal effects that occur in heterostructures under pulsed laser irradiation below the GaAs melting threshold lead to relaxation of mechanical stresses. At the initial stages of this process, the point defects appear in InxGa1−xAs/GaAs quantum wells. The latter lead to a “red” shift of the photoluminescence emission peaks of quantum wells and serve as centers of nonradiative recombination, which causes the quenching of the photoluminescence.

Surface state of CdTe crystals irradiated by KrF excimer laser pulses near the melting threshold

2003 ◽  
Vol 542 (1-2) ◽  
pp. 142-149 ◽  
Author(s):  
V.A. Gnatyuk ◽  
T. Aoki ◽  
Y. Nakanishi ◽  
Y. Hatanaka
Keyword(s):  
Excimer Laser ◽  
Surface State ◽  
Laser Pulses ◽  
Melting Threshold ◽  
Krf Excimer Laser

Overheating and Undercooling in Silicon During Pulsed-Laser Irradiation

1984 ◽  
Vol 35 ◽  
Author(s):  
B. C. Larson ◽  
J. Z. Tischler ◽  
D. M. Mills
Keyword(s):  
Pulsed Laser ◽  
Laser Pulses ◽  
High Energy ◽  
X Ray Diffraction ◽  
Laser Melting ◽  
Time Resolved ◽  
Synchrotron Source ◽  
X Ray ◽  
Krf Excimer Laser ◽  
Pulsed Laser Irradiation

ABSTRACTWe have used time-resolved x-ray diffraction measurements of thermal expansion induced strain to measure overheating and undercooling in <100> and <111> oriented silicon during pulsed laser melting and regrowth. 249 nm (KrF) excimer laser pulses of 1.2 J/cm2 energy density and 25 ns FWHM were synchronized with x-ray pulses from the Cornell High Energy Synchrotron Source (CHESS) to carry out Bragg profile measurements with ±2 ns time resolution. Combined overheating and undercooling values of 120 ± 30 K and 45 ± 20 K were found for the <111> and <100> orientations, respectively, and these values have been used to obtain information on the limiting regrowth velocities for silicon.

scholarly journals Воздействие импульсов эксимерного лазера на светоизлучающие InGaAs/GaAs-структуры с (Ga, Mn)As-слоем

2021 ◽  
Vol 63 (3) ◽  
pp. 346
Author(s):  
О.В. Вихрова ◽  
Ю.А. Данилов ◽  
Б.Н. Звонков ◽  
И.Л. Калентьева ◽  
Ю.М. Кузнецов ◽  
...  
Keyword(s):  
Energy Density ◽  
Quantum Well ◽  
Quantum Wells ◽  
Laser Annealing ◽  
Laser Energy ◽  
Laser Action ◽  
Pulsed Laser ◽  
Indium Content ◽  
Heat Propagation ◽  
Radiative Properties

It was studied the possibility of laser annealing modification of the properties of the (Ga,Mn)As layer located on the surface of a quantum-well InGaAs/GaAs structure, while retaining its radiative properties. The structures with four InGaAs/GaAs quantum wells (indium content was varied from 0.08 to 0.25), located at different distances from the (Ga,Mn)As layer, were fabricated by combining the methods of MOCVD-hydride epitaxy and pulsed laser deposition. The LPX-200 excimer laser pulse energy density was varied from 200 to 360 mJ/cm2, and the depth of laser action was determined from the change in the photoluminescence spectra of the quantum wells. In describing the results obtained, a model of the laser annealing process was used, based on solving the problem of heat propagation in a one-dimensional GaAs system, taking into account the (Ga,Mn)As layer on the surface. Changes in the structural and galvanomagnetic properties of the samples as a result of laser irradiation were analyzed. It is shown that as a result of pulsed laser action at a laser energy density range of 250 - 300 mJ/cm2, it is possible to preserve the emissive properties of the active region (InGaAs/GaAs quantum well) located at a distance of 10 - 12 nm from the (Ga,Mn)As layer and modify ferromagnetic properties of the semiconductor (Ga,Mn)As, namely: to increase the temperature of the ferromagnet-paramagnetic phase transition to values of at least 120 K. The results obtained are promising for the development of technology for devices of spin optoelectronics.

scholarly journals Role of dislocations in nitride laser diodes with different indium content

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Agata Bojarska-Cieślińska ◽  
Łucja Marona ◽  
Julita Smalc-Koziorowska ◽  
Szymon Grzanka ◽  
Jan Weyher ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Defect Density ◽  
Laser Diodes ◽  
Diffusion Path ◽  
Vapour Phase ◽  
Indium Content ◽  
Nonradiative Recombination ◽  
Light Emitters ◽  
Vapour Phase Epitaxy

AbstractIn this work we investigate the role of threading dislocations in nitride light emitters with different indium composition. We compare the properties of laser diodes grown on the low defect density GaN substrate with their counterparts grown on sapphire substrate in the same epitaxial process. All structures were produced by metalorganic vapour phase epitaxy and emit light in the range 383–477 nm. We observe that intensity of electroluminescence is strong in the whole spectral region for devices grown on GaN, but decreases rapidly for the devices on sapphire and emitting at wavelength shorter than 420 nm. We interpret this behaviour in terms of increasing importance of dislocation related nonradiative recombination for low indium content structures. Our studies show that edge dislocations are the main source of nonradiative recombination. We observe that long wavelength emitting structures are characterized by higher average light intensity in cathodoluminescence and better thermal stability. These findings indicate that diffusion path of carriers in these samples is shorter, limiting the amount of carriers reaching nonradiative recombination centers. According to TEM images only mixed dislocations open into the V-pits, usually above the multi quantum wells thus not influencing directly the emission.

scholarly journals High-quality percussion drilling with ultrashort laser pulses

2021 ◽  
Vol 127 (9) ◽  
Author(s):  
A. Feuer ◽  
R. Weber ◽  
R. Feuer ◽  
D. Brinkmeier ◽  
T. Graf
Keyword(s):  
Stainless Steel ◽  
Laser Fluence ◽  
Ablation Threshold ◽  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
High Quality ◽  
Edge Quality ◽  
Ultrashort Laser ◽  
Percussion Drilling

AbstractThe influence of the laser fluence on the quality of percussion-drilled holes was investigated both experimentally and by an analytical model. The study reveals that the edge quality of the drilled microholes depends on the laser fluence reaching the rear exit of the hole and changes with the number of pulses applied after breakthrough. The minimum fluence that must reach the hole’s exit in order to obtain high-quality microholes in stainless steel was experimentally found to be 2.8 times the ablation threshold.

N-Representable one-electron reduced density matrices reconstruction at non-zero temperatures

2021 ◽  
Vol 77 (5) ◽  
Author(s):  
Yoann Launay ◽  
Jean-Michel Gillet
Keyword(s):  
Density Matrix ◽  
Thermal Effects ◽  
Scattering Data ◽  
Temperature Dependent ◽  
Density Matrices ◽  
Reduced Density Matrices ◽  
Structure Factors ◽  
Reduced Density ◽  
Statistical Noise

This article retraces different methods that have been explored to account for the atomic thermal motion in the reconstruction of one-electron reduced density matrices from experimental X-ray structure factors (XSF) and directional Compton profiles (DCP). Attention has been paid to propose the simplest possible model, which obeys the necessary N-representability conditions, while accurately reproducing all available experimental data. The deconvolution of thermal effects makes it possible to obtain an experimental static density matrix, which can directly be compared with theoretical 1-RDM (reduced density matrix). It is found that above a 1% statistical noise level, the role played by Compton scattering data becomes negligible and no accurate 1-RDM is reachable. Since no thermal 1-RDM is available as a reference, the quality of an experimentally derived temperature-dependent matrix is difficult to assess. However, the accuracy of the obtained static 1-RDM, through the performance of the refined observables, is strong evidence that the Semi-Definite Programming method is robust and well adapted to the reconstruction of an experimental dynamical 1-RDM.

scholarly journals Laser-Induced Growth of Titanium Nitride Microcolumns on Biased Titanium Targets

2005 ◽  
Vol 20 (1) ◽  
pp. 62-67 ◽  
Author(s):  
E. György ◽  
A. Pérez del Pino ◽  
P. Serra ◽  
J.L. Morenza
Keyword(s):  
Bias Voltage ◽  
Single Pulse ◽  
Laser Pulses ◽  
High Repetition Rate ◽  
Applied Bias ◽  
Applied Bias Voltage ◽  
Surface Microrelief ◽  
High Repetition ◽  
Melting Threshold ◽  
Biased Samples

Titanium targets with a bias voltage ranging from −500 to +500 V were submitted to multipulse high repetition rate Nd:yttrium aluminum garnet (YAG; λ = 1.064 μm, τ ∼ 300 ns, ν = 30 kHz) laser irradiations in nitrogen at intensity values below the single-pulse melting threshold. The morphology of the TiN structures formed under the cumulative action of the laser pulses on the surface of the unbiased and biased targets was investigated by profilometry and scanning electron microscopy. Under these irradiation conditions, a specific columnar surface microrelief developed. The height of the microcolumns reached about 10–15 μm, and their diameter about 1–2 μm. The development of TiN microcolumns was enhanced by the applied bias voltage. The enhancement in the negative biased samples was stronger than that in the positive biased ones.

Al x Ga1− x N-Based Quantum Wells Fabricated on Macrosteps Effectively Suppressing Nonradiative Recombination

2018 ◽  
Vol 7 (2) ◽  
pp. 1801106 ◽  
Author(s):  
Minehiro Hayakawa ◽  
Shuhei Ichikawa ◽  
Mitsuru Funato ◽  
Yoichi Kawakami
Keyword(s):  
Quantum Wells ◽  
Nonradiative Recombination

Doping and crystallization of amorphous SiGe films with an excimer (KrF) laser

1995 ◽  
Vol 10 (8) ◽  
pp. 1884-1888 ◽  
Author(s):  
S. Krishnan ◽  
M.I. Chaudhry ◽  
S.V. Babu
Keyword(s):  
Silicon Germanium ◽  
Room Temperature ◽  
Laser Pulses ◽  
Laser Exposure ◽  
Silicon Substrates ◽  
A Value ◽  
Crystal Film ◽  
Krf Laser ◽  
Amorphous Silicon Germanium

Amorphous silicon germanium (a-SiGe) films, deposited on silicon substrates at room temperature in a molecular beam epitaxy system, were transformed into a single-crystal film and doped with phosphorus by exposure to KrF laser pulses. Electron channeling patterns showed that laser exposure resulted in crystallization of the undoped a-SiGe films. The SiGe films were doped by laser irradiation, using a phosphorus spin-on-dopant. The sheet resistance of the doped films decreased with increasing numbers of pulses, reaching a value of about ∼ 5 × 104 ohms/□ after 15 pulses. I-V data from mesa-type n-SiGe/p-Si diode devices were used to determine the effect of laser processing on the quality of the SiGe films.

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