Resonant Raman scattering at the saddle-point singularity inInxGa1

Optical characterization of pseudomorphic AlGaAs/InGaAs/GaAs heterostructures

“…We have also observed the peak corresponding to the AlAs-like LO phonon at ν = 365 cm -1 which is broad and strongly weaker than that at ν = 285 cm -1 . The feature at ν = 270 cm -1 is contributed by different modes: the TO phonon of GaAs due to the alignment of measurement is slightly out of the backscattering geometry, observed also in the resonant Raman scattering from mixed In y Ga 1-y As crystals [21]; the coupled LO phononplasmon mode Lobserved, both in n-type Al x Ga 1-x As [19], and in the InAs epilayer with the carrier concentration 1.0⋅10 17 cm -3 [22]. The deconvolution of the superimposed features in the spectral region 280-300 cm -1 and subsequent analysis of the Raman line shape was performed using the technique developed by Mintairov and Temkin [18].…”

“…The peak around 160 cm -1 was first reported by Kakimoto and Katoda [22] when the Raman spectra from Ga 1-x In x As epitaxial layers of various compositions were studied and was considered as the disorder-activated longitudinal acoustic (DALA) phonon of Ga 1-x In x As, because its intensity was at maximum near the middle-range composition. Then the DALA phonon was identified in the resonant Raman scattering at the saddle-point singularity in In x Ga 1-x As which was of a very weak intensity at the 2.41 eV laser energy, but become enhanced near the E 1 gap for the In 0.24 Ga 0.76 As sample [21]. In the case of In 0.53 Ga 0.47 As this feature was observed as a strong one far from resonance and become further enhanced near the E 1 gap.…”

Phonons in strained In1−xGaxAs/InP epilayers

“…[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Our polarized spectra are very similar to those reported by Pearsall et al 8 and Estrera et al, 18 except that the relative band intensities have changed because of the use of a quasibackscattering geometry in our case compared with the true backscattering geometry of Pearsall et al and Estrera et al In our scattering geometry for X(Y X)Y polarization, LO phonons are expected to dominate the spectrum, while for X(Y Z)Y polarization transverse optical ͑TO͒ modes are allowed. Because of the quasibackscattering geometry employed here, some mixing of TO modes into the LO mode spectrum can be expected.…”

Phonons inIn0.53Ga0.47As/IRowell1, Yu2, Lockwood3 et al. 2003Phys. Rev. B7000View full textAdd to dashboardCite

“…3,4 These techniques can also provide information on the atomic structure of the heterointerfaces and on confinement effects in very thin layers. 3,4 There have been many infrared [5][6][7][8][9][10][11][12][13][14][15][16][17][18] and Raman [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] investigations of the In 1Ϫx Ga x As alloy, principally in the form of strained ͑thin͒ or relaxed ͑thick͒ epilayers grown on GaAs or InP. However, there are wide differences among these investigations not only in the concentration dependence of the optical phonon frequencies but also in the number of modes observed and their origin ͑see, for example, Adachi 34 and Nash et al 35 ͒.…”