Model dielectric function spectra of GaAsN for far-infrared and near-infrared to ultraviolet wavelengths

Abstract

We study the optical properties of tensile strained GaAs1−yNy (0%⩽y⩽3.7%) single layers for photon energies from 0.75 to 4.5 eV and for wave numbers from 100 to 600 cm−1 using spectroscopic ellipsometry. The intentionally undoped GaAsN layers were grown pseudomorphically on top of undoped GaAs buffer layers deposited on Te-doped (001) GaAs substrates by metalorganic vapor phase epitaxy. We provide parametric model functions for the dielectric function spectra of GaAsN for both spectral ranges studied here. The model functions for photon energies from 0.75 to 4.5 eV excellently match dielectric function data obtained from a numerical wavelength-by-wavelength inversion of the experimental data (point-by-point fit). Critical-point analysis of the point-by-point fitted dielectric function is performed in the spectral regions of the fundamental band gap and the critical-point transitions E1 and E1+Δ1. The band-gap energy is redshifted whereas the E1 and E1+Δ1 transition energies are blueshifted with increasing y. For y⩽1.65% the observed blueshift of the E1 energy is well explained by the sum of the effects of biaxial (001) strain and alloying. The GaAsN layers show a two-mode phonon behavior in the spectral range from 100 to 600 cm−1. We detect the transverse GaAs- and GaN-sublattice phonon modes at wave numbers of about 267 and 470 cm−1, respectively. The oscillator strength of the GaN-sublattice resonance increases linearly due to alloying and tensile strain. We compare our results from the single layers with those obtained previously from tensile and compressively strained GaAsN/GaAs and GaAsN/InAs/GaAs superlattices.

Investigation of optical phonons and electronic properties of group III‐V nitride multi quantum wells by using far infrared magnetoplasmon spectroscopy

“…For numerical calculation, the Composition dependence of the optical phonon mode is calculated by the modified random element isodisplacement model (MREI) [5,6] for Al x Ga 1-x N and GaN x As 1-x with zincblend and wurtzite structure and there is good agreement between our results and limited data obtained from infrared reflectivity for ternary alloy GaNAs [7,8] and AlGaN [6,9] and effective masses of electrons and holes in GaNAs and AlGaN layers [10,11], respectively. In Fig.…”

Ellipsometry and Its Applications in Stoichiometry

“…Ignoring strain effects, the experimental data can be fitted, using E 1 GaN =7.0 eV, by E 1 GaN =2.901+2.363×10 -2 x+1.74×10 -4 x 2 (eV) with the N concentration given in %. Similar results have also been reported by other authors [102,103].…”

Progress in spectroscopic ellipsometry: Applications from vacuum ultraviolet to infrared

“…11͑b͒, was matched with this model to determine composition and strain information from the structure. 49 Other compound semiconductors have been investigated with IR-SE: InGaAsSb, 50 GaAsN, 51 InGaAsN, 52 GaNP, 53 and AlGaInP. 54 Superconductive YBaCuO 55 and YPrBaCuO 56 have also received recent attention with IR-SE.…”