Phonons in Low-dimensional Semiconductors

Project Summary

We have studied phonon spectra in III-V semiconductor superlattices (GaAs/AlAs, GaAs/InP) using empirical lattice dynamics models (valence Force Field Model, Rigid Ion model) and Green function techniques to obtain  phonon Local Density of States (LDOS). Emphasis has been given to the effect of atomic-scale interface disorder on the confined superlattice modes that are easily detected by Raman spectroscopy. Different types of interface defects have been studied, such as one-dimensional steps and interdiffused atoms. The role of interface disorder has been demonstrated to be responsible for the discrepancies in the phonon frequencies of the near zone edge phonon modes obtained by neutron scattering from bulk samples and Raman spectra from superlattices. Our work has demonstrated the weakness of the "unfolding" process based on Raman measurements to obtain bulk phonon frequencies from Raman measurements of high order  confined modes in superlattices.

Selected Publications

D. Kechrakos, P. R. Briddon and J. C. Inkson,

Effect of interface disorder on the confined phonon modes of GaAs/AlAs superlattices,

 Phys. Rev. B 44, R9114-9117 (1991)

D. Kechrakos and J. C. Inkson,

Phonons at non-planar (III-V) semiconductor heterojunctions : GaSb/InAs(001),

 Sem. Sci. Tech., 6, 155-159 (1991)

D. Kechrakos and J. C. Inkson,

Phonons at non-planar (III-V) semiconductor heterojunctions : GaAs/AlAs(001),

Sem. Sci. Tech., 5, 818-823 (1990)