MBE growth and Raman analysis of [hhk]GaAs/(Si or CaF2) highly strained hetero-structures (original) (raw)
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Applied Sciences, 2019
Raman scattering is an effective tool for the investigation of the strain state of crystalline solids. In this brief review, we show how the analysis of the GaAs-like longitudinal optical phonon frequency allowed to map the strain behavior across interfaces in planar heterostructures consisting of GaAsN wires embedded in GaAsN:H matrices. Moreover, we recently showed how the evolution of the longitudinal optical frequency with increasing H dose strongly depends on polarization geometry. In a specific geometry, we observed a relaxation of the GaAs selection rules. We also present new results which demonstrate how laser irradiation intensity–even at low levels–may affect the line shape of the GaAs-like spectral features in GaAsN hydrogenated materials.
Overgrowth and strain in MBE-grown GaAs/ErAs/GaAs structures
Journal of Crystal Growth, 1991
The molecular-beam epitaxial overgrowth of GaAs on single ErAs layers of varying thickness is studied, as well as the growth of, and strain accommodation in, ErAs/GaAs multilayer films on GaAs substrates. Resonant Raman scattering and Rutherford backscattering are used to characterize the crystal quality of overgrown GaAs layers, while Fourier-transform infrared absorption spectra of the crystal-field-split Er 3~intra 4f-shell transitions, at 1.54~m, are exploited as a novel probe of strain accommodation in the ErAs layers. Overgrowth of GaAs of good crystal quality on ErAs, as well as growth of ErAs/GaAs multilayer structures, are both demonstrated, but only for ErAs layers less than about 5 monolayers in thickness. Such thin ErAs layers are found to be tetragonally distorted due to elastic strain accommodation. Single buried ErAs films are found to be electrically continuous down to a thickness of 5 monolayers.
Raman scattering in (111) strained heterostructures
Microelectronics Journal, 1995
III-V based strained heterostructures grown along [hhk] directions are considered. The proportionality coefficients between the in-plane strain and the shift in the TO and LO phonon frequencies have been calculated from the elastic constants and phonon deformation potentials. GaAs/GaP (111) and GaAs/InP (111) systems, where the GaAs epitaxial layers are in compressive or tensile strain, respectively, have been grown by MOVPE at different times on A and B substrates and investigated by Raman scattering. The corresponding red or blue shifts of the frequencies of the LO and TO phonons are measured and the residual strain parallel to the interface is estimated. The Raman results are discussed on the basis of the morphology of the epilayer investigated by atomic force microscopy.
Microscopic structure of strained heterostructures
Solid-State Electronics, 1996
Extended X-ray absorption fine structure spectroscopy has been used to investigate the microscopic structure of InGaAs pseudomorphically grown on a (0Ol)GaAs substrate. The measure is restricted to the quasi-surface region of the epitaxial growth by means of the glancing-angle technique. The results show that the strain is accommodated by bond-stretching and bond-bending and that the lattice expands in the growth direction within the limits previewed by the elastic theory.
Determination of in-depth thermal strain distribution in Molecular Beam Epitaxy GaAs on Si
Applied Physics A Solids and Surfaces, 1991
In-depth stress distribution GaAs layers grown by Molecular Beam Epitaxy (MBE) on Si (001) has been studied by X-ray diffraction, photoluminescence and Raman spectroscopy. In order to determine the stress state at different distances to the interface GaAs/Si, layers of different thickness were prepared by chemical etching of the grown samples. We observe a non-uniform residual strain distribution through the GaAs on Si epilayer. Residual strain of thermal origin is larger in the highly defective region (,-~ 0.4 gm) near the GaAs/Si interface where we have found a non-elastic relation between measured in-plane (all) and in growth direction (a±) lattice parameters. However, thermal strain is partially relaxed by formation of 107 cm -2 dislocations in the region of better crystalline quality near the external surface.
Structural characterization techniques for the analysis of semiconductor strained heterostructures
Mikrochimica Acta, 1994
A combined method for structural characterization of strained epitaxial heterostructures involving different techniques such as Rutherford backscattering spectrometry (RBS), multiple crystal X-ray diffractometry (MCD) and transmission electron microscopy (TEM) is presented. In order to obtain a complete characterization of the analysed structure, three different quantities are measured independently: the epilayer thickness, the density of misfit dislocations which may appear at the interface, and the significant components of the strain tensor, mainly the tetragonal distortion, affecting the epilayer lattice. In this way the thermodynamic state and the mechanisms of plastic deformation of the structures can be fully investigated. In this contribution we present and discuss the experimental results concerning a set of InP/GaAs samples having different layer thicknesses ranging from 5 to 500 nm. The thickness of the samples has been determined by RBS. Measurements of in-plane strain and tetragonal distortion have been performed by MCD and RBSchannelling respectively, finally TEM has been used for determining the defects densities and distribution.
Growth of strained GaAs1−ySby layers using metalorganic vapor phase epitaxy
Journal of Crystal Growth, 2007
The growth of pseudomorphically strained GaAs 1Ày Sb y layers with high Sb-mole fractions of yX0.35 are desired on GaAs substrates for making lasers and detectors in the mid-infrared range. The effect of gas-phase precursor chemistry on the strained-layer Sbincorporation efficiency in metalorganic vapor phase epitaxy (MOVPE) was determined using four combinations of ethyl-and methyl-Ga and Sb precursors. The Sb-mole fractions in the strained GaAs 1Ày Sb y layers were found to be lower than those in relaxed films due to the strain-induced 'lattice-latching' effects. The Sb-mole fraction in the strained GaAs 1Ày Sb y layers decreased with the increasing AsH 3 / Ga ratio for all the precursor chemistries. Higher Sb-incorporation efficiencies were observed for the ethyl-Ga chemistries. The experimental results were discussed in terms of lattice-latching effects, Sb-segregation phenomena and different decomposition kinetics for various precursor chemistries.
Application Raman scattering studies of strain effects in (100) and (311)B GaAs12xBix
JOURNAL OF APPLIED PHYSICS 114, 193516 (2013)
We report room-temperature Raman studies of strained (100) and (311)B GaAs1xBix epitaxial layers for x0.039. The Raman spectra exhibit a two-mode behavior, as well as disorder-activated GaAs-like phonons. The experimental results show that the GaAs-like LO(C) mode experiences a strong composition-dependent redshift as a result of alloying. The peak frequency decreases linearly from the value for pure GaAs (293 cm1) with the alloyed Bi fraction x and the introduced in-plane lattice strain ek, by DxLO ¼ Dxalloy Dxstrain. X-ray diffraction measurements are used to determine x and ek allowing Dxalloy to be decoupled and is estimated to be 12(64) cm1/x for (100) GaAs1xBix. DxLO is measured to be roughly double for samples grown on (311)B-oriented substrates to that of (100) GaAs. This large difference in redshift is accounted for by examining the Bi induced strain, effects from alloying, and defects formed during high-index (311)B crystal growth.