Phonon properties of (311) GaAs/AlAs superlattices (original) (raw)
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Phonon properties of GaAs/AlAs superlattice grown along the [110] direction
Physical Review B, 1989
We report Raman scattering studies of GaAs/A1As superlattices grown along the [110]direction. The appearance of distinct x-ray satellite peaks around the Bragg reflections demonstrates the formation of highly ordered periodic superlattice structures. The confined-optical-phonon modes corresponding to the three optical bulk branches as well as the folded-acoustic-phonon modes are observed. The confined modes have frequencies which map closely onto those of the optical phonons of the parent materials in the [110]direction (I-K-X) of k space. We also observe resonant Raman scattering by confined-optical and in-plane (interfacelike) vibrational overtones and their combinations. The results of a lattice-dynamical calculation for this superlattice is also presented with special emphasis on angular dispersion and the mixed polarization of superlattice modes.
Phonons in GaAs/AlAs superlattices grown along the [111] direction
Physical Review B, 1990
We present Raman-scattering data for GaAs/AlAs superlattices grown on GaAs substrates along the [111]direction. The appearance of distinct x-ray satellite peaks around the Bragg reflections demonstrates the formation of highly ordered periodic superlattice structures. The confined optical-phonon modes have frequencies which map closely those of the parent materials in the [111] direction of k space. We also observe folded acoustic-phonon modes. The results of a latticedynamical calculation for these superlattices on the basis of the shell model are presented, with special emphasis on the angular dispersion of "interface" modes.
Confined longitudinal and transverse phonons in GaAs/AlAs superlattices
Superlattices and Microstructures, 1986
The phonon spectrum of GaAs/AIAs superlattices along the (001) growth direction is calculated using a new approach based on a realistic unified treatment of the interactions in both bulk constituents, which naturally lends itself to dealing with superlattice geometries. Results for a (GaAs)3(AIAs)3 superlattice are shown with emphasis on different aspects of confinement.
Phonon dispersion curves of GaAs-AlAs superlattices grown in the [111] and [110] directions
Physical Review B, 1989
The phonon properties of (GaAs),(AlAs), superlattices are studied with an eleven-parameter rigid-ion model. Short-range interactions up to the second neighbours are included, and the long-range Coulomb interaction is calculated exactly. Modes propagating both normal (k/l = 0) and oblique (k/l # 0) to the interfaces are studied. Anisotropy of sane center optical phononu is examined. The theoretical results are compared with the existing experimental data with favorable agreement .
Phonon spectra of ultrathin GaAs/AlAs superlattices: An ab initio calculation
Phonon spectra of ultrathin (GaAs), (A1As)"(001) superlattices are studied theoretically using linear-response density-functional techniques. Results are presented for n 1,2, 3 superlattices, along with prototype superce11 calculations aimed at simulating a completely disordered (alloy) as well as some partially disordered superlattices. Besides interfacial disorder, which modifies the effective confinement length of low-order longitudinal-optic phonons, we find thatin the ultrathin regimesome degree of cationic mixing must also affect inner planes in order to explain experimental findings. ' This is so becausein a two-mode alloy such as GaAlAsthe Ga(Al) ions do not participate in the vibration of A1As-(GaAs-) like modes, and therefore give no contribution to the corresponding polarization.
Phonon dispersion curves of GaAs/AlAs superlattices
Superlattices and Microstructures, 1988
The phonon properties of (GaAs)m(AlAs)n superlattices are studied with an eleven-parameter rigid-ion model. Short-range interactions up to the second neighbours are included, and the long-range Coulomb interaction is calculated exactly. Modes propagating both normal (k// = 0) oblique (k// ≡ 0) to the interfaces are studied. Anisotropy of zone center optical phonons is examined. The theoretical results are compared with the existing experimental data with favorable agreement.
Phonon modes of short-period (GaAs)n/(AlAs)n superlattices
2002
In the work finding optical phonon energies from photoluminescence spectra and interpretation of their dependence on quantum well width are carried out. Remarkable decreasing both GaAs and AlAs phonon energies has been observed. It is shown that this dependence differs noticeably from that obtained from Raman spectra. The possible origin of this phenomenon is considered. 2002 Published by Elsevier Science B.V. PACS: 78.66.-w; 78.55.Cr; 63.22.+m Keywords: Short-period superlattice; Photoluminescence; Longitudinal optical phonon; Confined mode; Γ -X transfer 0375-9601/02/$ -see front matter 2002 Published by Elsevier Science B.V. PII: S 0 3 7 5 -9 6 0 1 ( 0 2 ) 0 0 0 1 6 -6
Solid State Communications, 1992
We present results of resonant Rarnan scattering on a series of ultrashort-period (GaAs)J(AIAs)~ superlattices with 1 _~ n _ 5. The frequencies of confined longitudinal optical phonons of both GaAs and AIAs are compared with recent ab initio calculations and mapped onto the bulk dispersion curve. The concept of unfolding is also found valid for ultrashort-period superlattices. The frequency dependence of the first confined phonon of GaAs and AIAs on layer thickness is well described by these ab initso calculations when inter[ace disorder is taken into account. In all samples we observe second-order difference scattering from combinations of GaAs and AIAs optical phonons. The measurement of resonance profiles at various temperatures demonstrates that this scattering originates from second-order processes. The width and position of this difference scattering are explained by considering all possible combinations of the GaAs and AIAs longitudinal optical (LO), transverse optical (TO) and interface (IF) phonons.
Pressure dependence of phonon modes in GaAs/AlAs superlattices
Physical Review B, 1989
Brillouinand Raman-scattering measurements on @ GaAs-AlAs superlattice have been performed as a function of the hydrostatic pressure up to 160 kbar. Below 110kbar the acoustic folded and optical confined phonons have been measured, and the results are compared to the predictions of the actual models. Beyond 110 kbar the AlAs layers undergo a phase transition which is analyzed and discussed in comparison to previous results.