MBE growth and Raman analysis of [hhk]GaAs/(Si or CaF2) highly strained hetero-structures (original) (raw)
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.
Raman-strain relations in highly strained Ge: Uniaxial ⟨100⟩, ⟨110⟩ and biaxial (001) stress
Journal of Applied Physics, 2017
The application of high values of strain to Ge considerably improves its light emission properties and can even turn it into a direct band gap semiconductor. Raman spectroscopy is routinely used for strain measurements. Typical Raman-strain relationships that are used for Ge were defined up to $1% strain using phonon deformation potential theory. In this work, we have studied this relationship at higher strain levels by calculating and measuring the Raman spectral shift-strain relations in several different strain configurations. Since differences were shown between the usual phonon deformation potential theory and ab-initio calculations, we highlight the need for experimental calibrations. We have then measured the strain in highly strained Ge micro-bridges and micro-crosses using Raman spectroscopy performed in tandem with synchrotron based microdiffraction. High values of strain are reported, which enable the calibration of the Raman-strain relations up to 1.8% of in plane strain for the (001) biaxial stress, 4.8% strain along h100i, and 3.8% strain along h110i. For Ge micro-bridges, oriented along h100i, the nonlinearity of the Raman shift-strain relation is confirmed. For the h110i orientation, we have shown that an unexpected non-linearity in the Raman-strain relationship has also to be taken into account for high stress induction. This work demonstrates an unprecedented level of strain measurement for the h110i uniaxial stress and gives a better understanding of the Raman-strain relations in Ge.
Determination of band offsets in strained-Si heterolayers
Thin Solid Films, 2004
Strained-Si/SiGe/Si structures are of increasing importance for microelectronic applications. A fully relaxed-SiGe buffer layer is required for growing strained-Si for applications towards high performance field effect transistors (FETs) having strained-Si as the channel. Preparation of epitaxial strained-Si layers on relaxed-SiGe (001) heterostructures using low pressure chemical vapor deposition (LPCVD) is reported. Gas source molecular beam epitaxy (GSMBE) grown strained-Si films are used to compare with LPCVD strained-Si films. Characterization of the strained-Si layers has been performed using AFM, TEM and Raman spectroscopy. Conduction and valence band offsets of strained-Si on relaxed-SiGe heterostructures have been extracted from measured capacitance -voltage (C -V) profiling of MOS capacitors fabricated on strained-Si using SiO 2 as the dielectric. Extracted experimental values of the valence and conduction band offsets are in good agreement with theoretical predictions. D
Relaxation of strain in patterned strained silicon investigated by UV Raman spectroscopy
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2006
Tensile strained Si (sSi) layers were epitaxially deposited onto fully relaxed Si 0.78 Ge 0.22 (SiGe) epitaxial layers (4 m) on silicon substrates. Periodic arrays of 150 nm × 150 nm and 150 nm × 750 nm pillars with a height of 100 nm were fabricated into the sSi and SiGe layers by electronbeam lithography and subsequent reactive ion etching. The strain in the patterned and unpatterned samples was analyzed using high-resolution UV micro-Raman spectroscopy. The 325 nm excitation line used probes strain in Si close to the surface (penetration depth of ∼9 nm). The Raman measurements revealed that the nano-patterning yields a relaxation of strain of ∼33% in the large pillars and ∼53% in the small pillars of the ∼0.95% initial strain in the unpatterned sSi layer.
Bulletin of Materials Science, 2019
GaAs 1−x−y N x Bi y is a suitable candidate for 1.06 µm solid state lasers and high-efficiency solar cells. Mathematical models such as 16-band kp model is used to study the band structure, strain generated effect, band offset and variation of their parameters with Bi and N concentrations. Lattice constants of alloy GaAs 1−x−y N x Bi y with x/y = 0.58 can match those of GaAs with the incorporation of Bi and N into GaAsNBi. Arsenic atom substitution due to the incorporation of N and Bi impurity atoms causes a significant band gap reduction of ∼200 meV for GaAs 0.937 N 0.023 Bi 0.04 alloys under lattice-matched conditions and in addition, by tuning the concentrations of N and Bi, the electrical and optical properties of GaAsNBi can be controlled. Optical gain of GaAs 1−x−y N x Bi y quantum well (QW) and GaAs as a barrier are calculated in generalized mode and observed the effect of the energy level of GaAs barrier on the GaAsNBi QW. Keywords. GaAs 1−x−y N x Bi y ; kp method; strain; optical gain.
Strained-Si heterostructure field effect transistors
Semiconductor Science and Technology, 1998
The purpose of this review article is to report on the recent developments and the performance level achieved in the strained-Si/SiGe material system. In the first part, the technology of the growth of a high-quality strained-Si layer on a relaxed, linear or step-graded SiGe buffer layer is reviewed. Characterization results of strained-Si films obtained with secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy, spectroscopic ellipsometry and Raman spectroscopy are presented. Techniques for the determination of bandgap parameters from electrical characterization of metal-oxide-semiconductor (MOS) structures on strained-Si film are discussed. In the second part, processing issues of strained-Si films in conventional Si technology with low thermal budget are critically reviewed. Thermal and low-temperature microwave plasma oxidation and nitridation of strained-Si layers are discussed. Some recent results on contact metallization of strained-Si using Ti and Pt are presented. In the last part, device applications of strained Si with special emphasis on heterostructure metal oxide semiconductor field effect transistors and modulation-doped field effect transistors are discussed. Design aspects and simulation results of n-and p-MOS devices with a strained-Si channel are presented. Possible future applications of strained-Si/SiGe in high-performance SiGe CMOS technology are indicated.