0000000000278217
AUTHOR
F. Demangeot
showing 5 related works from this author
Splitting of surface-related phonons in Raman spectra of self-assembled GaN nanowires
2012
cited By 2; International audience; Micro Raman spectroscopy studies have been performed on GaN nanowires grown by Plasma-Assisted Molecular Beam Epitaxy on Silicon (111) substrate. From the analysis of experimental data, the emergence of a two peaks band located near 700 cm-1 has been attributed to the Raman scattering by surface-related phonons. We have analyzed the surface character of these two modes by changing the dielectric constant of the exterior medium and some experimental parameters. Furthermore, a theoretical model describing the nanowires ensemble by means of an effective dielectric function has been used to interpret the Raman scattering results. Those numerical simulations a…
Anticrossing of axial and planar surface-related phonon modes in Raman spectra of self-assembled GaN nanowires
2012
cited By 17; International audience; GaN columnar nanostructures usually called nanowires have been investigated by micro-Raman spectroscopy. In addition to conventional Raman scattering by confined optical phonons of a wurtzite structure (i.e., E 2h and QLO modes), an unusual two peaks band centered near 700 cm -1 is observed and analyzed as a function of several experimental parameters (polarization, filling factor, incidence angle). The surface character of these two modes is experimentally confirmed by their high sensitivity to the dielectric constant of the as-grown nanowires surrounding medium. Calculations describing the nanowires' environment by means of an effective dielectric func…
Resonant Raman scattering of core-shell GaN/AlN nanowires.
2020
Abstract We have analyzed the electron–phonon coupling in GaN/AlN core–shell nanowires by means of Raman scattering excited at various wavelengths in the ultraviolet spectral range (335, 325 and 300 nm) and as a function of the AlN shell thickness. The detailed analysis of the multi-phonon spectra evidences important differences with excitation energy. Under 325 and 300 nm excitation the Raman process is mediated by the allowed A 1(LO) phonon mode, where the atoms vibrate along the NW axis. Considering its selection rules, this mode is easily accessible in backscattering along the wurtzite c axis. Interestingly, for 335 nm excitation the scattering process is instead mediated by the E 1(LO)…
Current status of AlInN layers lattice-matched to GaN for photonics and electronics
2007
We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state- of- the- art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of ( 1 - 5) x 10(18) cm(-3) and a large Stokes shift (similar to 800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified …
Splitting of the surface phonon modes in wurtzite nanowires
2013
We analyze the surface optical modes of GaN nanowires (NW) and perform a comparative study with the characteristics expected for other polar NWs. The theoretical analysis of the modes is performed within the context of the effective medium theory that takes into account the dipolar interaction between neighboring NWs (Maxwell-Garnett approximation). It is shown that deviations of the exciting light from the NWs axis, which coincides with the wurtzite c-axis, result in the anticrossing of two distinct surface phonon branches, leading to their splitting in axial and planar components and the appearance of two peaks in the Raman spectra. Additional calculations are performed that determine th…