• Sujata Rath

      Articles written in Pramana – Journal of Physics

    • Effect of strain on vibrational modes in strained layer superlattices

      Sujata Rath Sankar P Sanyal

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      We have investigated the lattice vibrational properties of a two-component strained layer semiconductor superlattice (GaAs)n1 (GaSb)n2 using a one-dimensional linear chain model and transfer matrix method [1]. Effect of strain, arising due to the lattice mismatch (∼ 7%) has been considered explicitly in the equation of motion. We show for the first time that the optical vibrational frequency increases (in the case of (GaAs)4 (GaSb)n) or decreases (in the case of (GaAs)n(GaSb)4) with increase of layer thicknessn, in either type of superlattices. Raman scattering measurements on some other similar systems support our findings.

    • Phonon dispersion in quasiperiodic semiconductor superlattices

      Sujata Rath Prafulla K Jha Sankar P Sanyal

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      The phonon spectra of unstrained and strained quasiperiodic semiconductor superlattices (QSSL) have been calculated using one-dimensional linear chain model. We consider two types of quasiperiodic systems, namely cantor triadic bar (CTB) and Fibonacci sequences (FS), constituting of AlAs, GaAs and GaSb of which the latter two have a lattice mismatch of about 7%. The calculations have been made using transfer matrix method and also with and without the inclusion of strain. We present the results on phonon spectra of two component CTB and two as well as three component FS semiconductor superlattices (SSL), thickness and order dependence on LO mode of GaAs, effect of strain on LO frequency of GaAs. The calculated results show that the strain generated due to lattice mismatch reduces significantly the magnitudes of the confined optical phonon frequency of GaAs.

    • Phonon dispersion in aluminium arsenide and antimonide

      Prafulla K Jha Sujata Rath Sankar P Sanyal

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      The phonon dispersion curves for aluminium arsenide and antimonide have been investigated by using a deformation bond approximation model. The results obtained from this model are compared with the experimental values wherever it is available. Since there is no complete experimental phonon dispersion curves for AlAs, we could not compare our calculated results, but the results of AlSb have been compared with the inelastic neutron scattering measurements at 15 K. However, we compare the phonon frequencies of AlAs and AlSb at critical points of the Brillouin zone obtained by our calculations and Raman spectroscopy measurements. This model predicts the phonon modes satisfactorily in all the symmetry directions of the Brillouin zone (BZ). The spectrum has similar features as observed in other III–V compound semiconductors.

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