Antilocalization effect on photo-generated carriers in semi-insulating GaAs sample

The transient thermoreflectance (TTR) method consists of measuring changes in the reflectivity of a material (thin film) under pulsed laser heating, and relating these changes to the corresponding surface temperature variations. Analytical solutions of the diffusion problem are then used to determine the thermal conductivity of the material following an iterative matching process between the solutions and the experimental results. Analytical solutions are attainable either when the material absorbs the laser energy volumetrically or when the material absorbs the laser energy at the surface. Either solution allows for the determination of only one thermal property (thermal conductivity or diffusivity), with the other one assumed to be known. A new, single, analytical solution to the transient diffusion equation with simultaneous surface and volumetric heating, found using fractional calculus, is presented in a semi-derivative form. This complete solution provides the means to determine the two thermal properties of the material (thermal conductivity and diffusivity) concomitantly. In this preliminary study, the solution component for surface heating is validated by comparison with experimental data for a gold sample using the classical thermoreflectance method. Further results, for surface and volumetric heating, are obtained and analyzed considering a GaAs sample.

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Measurement of statistical nuclear spin polarization in a nanoscale GaAs sample

Physical Review B ◽

10.1103/physrevb.84.205328 ◽

2011 ◽

Vol 84 (20) ◽

Cited By ~ 10

Author(s):

Fei Xue ◽

D. P. Weber ◽

P. Peddibhotla ◽

M. Poggio

Keyword(s):

Spin Polarization ◽

Nuclear Spin ◽

Gaas Sample ◽

Nuclear Spin Polarization

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In-situ Measurement of GaAs Optical Constants and Surface Quality, as Functions of Temperature

MRS Proceedings ◽

10.1557/proc-222-87 ◽

1991 ◽

Vol 222 ◽

Author(s):

Huade Yao ◽

Paul G. Snyder

Keyword(s):

Room Temperature ◽

Optical Constants ◽

Molecular Beam ◽

Elevated Temperatures ◽

Native Oxide ◽

Time Data ◽

Gaas Sample ◽

Optical Thermometer ◽

Surface Changes

ABSTRACTIn-situ spectroscopic ellipsometry (SE) was applied to monitor GaAs (100) surface changes induced at elevated temperatures inside an ultrahigh vacuum (UHV) chamber (<1×10−9 torr base pressure, without As overpressure). The real time data showed clearly the evolution of the native-oxide desorption at ∼577°C, on a molecular-beam-epitaxy (MBE)-grown GaAs (100) surface. In addition, surface degradation was found before and after the oxide desorption. A clean and smooth surface was obtained from an arsenic-capped, MBE-grown GaAs sample, after the arsenic coating was evaporated at ∼350 °C inside the UHV. Pseudodielectric functions <ε>GaAs, from 1.6 eV to 4.5 eV, were obtained through the SE measurements, from this oxide-free surface, at temperatures ranging from room temperature (RT) to ∼610 °C. These <ε> data were used as reference data to develop an algorithm for determining surface temperatures from in-situ SE measurements, thus turning the SE instrument into a sensitive optical thermometer.

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Simultaneous Quantification of Indium and Nitrogen Concentration in InGaNAs Using HAADF-STEM

Microscopy and Microanalysis ◽

10.1017/s1431927614013051 ◽

2014 ◽

Vol 20 (6) ◽

pp. 1740-1752 ◽

Cited By ~ 16

Author(s):

Tim Grieb ◽

Knut Müller ◽

Emmanuel Cadel ◽

Andreas Beyer ◽

Marco Schowalter ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Strain State ◽

Nitrogen Concentration ◽

Energy Shift ◽

Dark Field ◽

Sources Of Information ◽

Gaas Sample ◽

Transmission Electron Microscopy Analysis ◽

Transmission Electron

AbstractTo unambiguously evaluate the indium and nitrogen concentrations in InxGa1−xNyAs1−y, two independent sources of information must be obtained experimentally. Based on high-resolution scanning transmission electron microscopy (STEM) images taken with a high-angle annular dark-field (HAADF) detector the strain state of the InGaNAs quantum well is determined as well as its characteristic HAADF-scattering intensity. The strain state is evaluated by applying elasticity theory and the HAADF intensity is used for a comparison with multislice simulations. The combination of both allows for determination of the chemical composition where the results are in accordance with X-ray diffraction measurements, three-dimensional atom probe tomography, and further transmission electron microscopy analysis. The HAADF-STEM evaluation was used to investigate the influence of As-stabilized annealing on the InGaNAs/GaAs sample. Photoluminescence measurements show an annealing-induced blue shift of the emission wavelength. The chemical analysis precludes an elemental diffusion as origin of the energy shift—instead the results are in agreement with a model based on an annealing-induced redistribution of the atomic next-neighbor configuration.

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A 6 Bit-0.5 GHz Full Nyquist GaAs Sample and Hold

10.1109/esscirc.1988.5468411 ◽

1988 ◽

Author(s):

A. Dubois ◽

M. Le Paih ◽

P. Martin ◽

C. Guiberteau ◽

M. Gloanec ◽

...

Keyword(s):

Gaas Sample ◽

Sample And Hold

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Raman and Ellipsometric Studies of Delta-Doped GaAs

MRS Proceedings ◽

10.1557/proc-261-57 ◽

1992 ◽

Vol 261 ◽

Author(s):

H. Yao ◽

E. F. Schubert ◽

R. F. Kopf

Keyword(s):

Spectroscopic Ellipsometry ◽

High Energy ◽

Plasmon Mode ◽

Gaas Sample ◽

Similar Frequency ◽

Layer Spacing ◽

Coupled Mode ◽

Spatial Quantization ◽

Electron Distributions ◽

Energy Subbands

ABSTRACTGaAs (100) samples with multiple δ-doped layers (N2D=∼2×1013/cm2) were studied by Raman scattering (RS) and spectroscopic ellipsometry (SE). A quasithree- dimensional (3D) plasmon-phonon coupled mode (L+), probed at λ= 514.5 nm, from a 9-layer δ-doped GaAs with layer-spacing of 100 Å, was observed at ∼895 cm−1. At similar frequency, a plasmon mode was also detected from another GaAs sample with the same δ-doping periods but doubled layer-spacing (200 Å). This provides evidence of spatial quantization of the electron distributions in δ-doped GaAs. The equivalent 3D electron concentration, estimated from the Raman plasmon mode, is ∼1.1×1019/cm3. The presence of the 3D plasmon mode from a quasi-two-dimensional (2D) electron gas is possibly contributed by the electrons in the high energy subbands in the V-shaped potential well of the δ-doped GaAs. The pseudodielectric function <ε>= <ε1>+i<ε2> of this δ-doped GaAs sample was measured by spectroscopic ellipsometry (SE), from an unoxidized surface in an ultrahigh vacuum (UHV) chamber, in the range of 1.5 to 5.0 eV. Compared with uniformly doped GaAs, our SE data indicates a reduced broadening of the optical transitions between the E1 and E1+Δ1, energies due to the δ-doping.

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Residual strain field in indented GaAs

Journal of Materials Research ◽

10.1557/jmr.2003.0203 ◽

2003 ◽

Vol 18 (6) ◽

pp. 1474-1480 ◽

Cited By ~ 9

Author(s):

Pascal Puech ◽

François Demangeot ◽

Paulo Sergio Pizani ◽

Samuel Wey ◽

Chantal Fontaine

Keyword(s):

Raman Spectroscopy ◽

Raman Scattering ◽

Residual Strain ◽

Strain Field ◽

Optical Phonons ◽

Gaas Sample ◽

Micro Raman Spectroscopy ◽

Atomic Force ◽

Microscope Images ◽

The One

This paper presents an optical mean to probe carefully the strain field generated by a microindentation on [111]-oriented GaAs sample, using micro-Raman spectroscopy and microphotoluminescence spectroscopy. Raman and photoluminescence signals recorded from the same point of the sample are directly compared. The frequency shift of the longitudinal and transverse optical phonons was analyzed in great detail, revealing unambiguously the presence of both compressive and tensile strains within the indented area. Outside the indentation fingerprint, the magnitude of strain deduced from luminescence measurements was found to be lower than the one determined by Raman scattering. The Raman spectra revealed significant variations of the optical phonons polarizability with the deformation. Finally, atomic force microscope images of the indented zone aid in the interpretation.

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An 8ns monolithic GaAs sample and hold amplifier

10.1109/isscc.1987.1157149 ◽

2005 ◽

Cited By ~ 1

Author(s):

R. Bayruns ◽

N. Scheinberg ◽

R. Goyal

Keyword(s):

Gaas Sample ◽

Sample And Hold

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IMPROVEMENT IN FIGURE OF MERIT BY DOPING FOR SQUEEZED STATE GENERATION IN GaAs

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s0218863501000772 ◽

2001 ◽

Vol 10 (04) ◽

pp. 377-387 ◽

Cited By ~ 2

Author(s):

PRATIMA SEN

Keyword(s):

Figure Of Merit ◽

Low Frequency ◽

Free Carrier Absorption ◽

Squeezed State ◽

Gaas Sample ◽

Electron Model ◽

State Generation ◽

Frequency Regime ◽

Carrier Absorption ◽

Frequency Laser

A simplistic theoretical investigation based upon the free electron model of optical nonlinearities has been made to establish the superiority of a doped semiconductor over its intrinsic counterpart in efficient squeezed state generation. Choice of Doping level at a given operating frequency regime has to be carefully choosen to avoid free carrier absorption and scattering losses. The relevant figure of merit is found to favor a doped crystal duly shined by off-resonant low frequency laser as a potential scheme to achieve significant quadrature variance. Numerical calculations have been made for GaAs sample irradiated with 10.6 μm pulsed CO 2 laser of intensity ~ 1.6 × 102 GW/m 2.

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