Raman scattering and optical-absorption studies of the metastable alloy systemGaAsxSb1

Abstract

The optical properties of GaAs"Sbl "alloys grown across the entire concentration range by multitarget sputter deposition are reported. X-ray diffraction, optical absorption, and Raman spectra show the samples to be single-crystal, single-phase alloys for all x, including those in the miscibility gap. Alloy lattice constants are found to vary linearly with concentration. The direct I -point energy gaps, determined from optical-absorption measurements, show significant negative bowing.Contrary to previous reports, the Raman spectra exhibit two-mode behavior throughout, including a local mode of As in GaSb and a resonant mode of Sb in GaAs. An analysis of peak frequencies and line shapes versus concentration is given in the context of disorder effects. %e observe broadenings much less severe and asymmetric than those seen in similar systems and usually interpreted in terms of k&0 density-of-states activation. The observed adherence to zone-center selection rules for all x, suggests a more accurate interpretation to be one involving the k =0 spectral projection of the density of states.

First-principles calculations of the electronic and structural properties of GaSb

“…These values are summarized in table, along with their respective percentages of error for each of the functionals. It was clearly observed that the functionals MBJ and RTPSS showed the lowest percentages of error when being compared to the experimental values reported in the literature [26]. In addition, we note the tendency that the approximations LDA and GGA greatly underestimate the band gap energy of the GaSb compound, as it has been observed in other type III-V semiconductors.…”

“…The variations found for the prediction of the band-gap energy (E gap ) of the diverse functionals is owed to the approximations that were done in the DFT, at the end of the energy of exchange-correlation, underestimate this value. This is a known error of DFT [26,27] 232.6−237 (ΓLO) [26,27] Table, the values of the structural parameters (a, B 0 ) and the energy of cohesion (E coh ) can be observed, obtained using eight different functionals: LDA, PBE, PBEsol, PW91, rPBE, AM05, TPSS and RTPSS. The reported values are in accordance with the experimental [25] and theoretical [24] data reported by other authors.…”

Raman spectroscopy of self-catalyzed GaAs1−xSbxnanowires grown on silicon

“…org/Nano/24/405707/mmedia). For comparison purposes, we have also plotted the alloy mode dependence found by McGlinn et al on GaAs 1−x Sb x thin films epitaxially grown on GaAs substrates [24]. In this work it was shown that the GaAs 1−x Sb x alloy system exhibits a two-mode behavior.…”

“…This gives impurity mode frequencies of 251 cm −1 and 242 cm −1 for GaSb:As and GaAs:Sb, respectively, fitting relatively well to what has been measured. We have used this estimation for GaAs:Sb, while for GaSb:As we have adjusted it to the experimental value of ∼241 cm −1 [8,24]. On the other hand, following the theory of ionic plasmon coupling as described in [25], the dielectric function of an alloy is expressed as:…”

“…LO modes are generally more sensitive to electric fields). Under the virtual crystal approximation (VCA), an alloy such as GaAs 1−x Sb x can be treated like a continuum in the macroscopic scale whose physical properties linearly depend on the alloy composition, such as the lattice parameters and bond force constant (f ) [24]. Thus, within the harmonic approximation, the square of the TO frequency will linearly shift from the frequency of the pure binary (i.e., GaAs) to the impurity mode of the oscillator surrounded by the other binaries (i.e., Ga-As in a GaSb matrix).…”