Confined acoustic and propagating optical phonons in GaN/Ga1-xAlxN superlattices |
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| Affiliation: | 1. Donostia International Physics Center (DIPC), San Sebastián/Donostia, Basque Country 20018, Spain;2. Dipartimento di Scienza dei Materiali, Universitá di Milano-Bicocca, Milano 20125, Italy;3. Departamento de Física de Materiales UPV/EHU, Centro de Física de Materiales CFM - MPC and Centro Mixto CSIC-UPV/EHU, San Sebastián/Donostia, Basque Country 20018, Spain;4. Karlsruher Institut für Technologie, Institut für Festkörperphysik, P.O. Box 3640, Karlsruhe 76021, Germany;5. Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 17, Göttingen 37077, Germany |
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| Abstract: | The lattice vibrations in GaN/Ga1-xAlxN(001) superlattices are studied within a rigid-ion model. The elastic forces are characterized by a generalized three-parameter Keating model, whereas the microscopic electric field is fully included via an Ewald summation. The composition and the disorder in the barriers are described within a generalized REI model. Cubic symmetry is assumed for each single material layer in the superlattice. In contrast to the GaAs/Ga1-xAlxAs case we observe a confinement of the acoustic phonons in the frequency region between the zone-boundary phonons of GaN and AlN. In the region of optical phonons both propagating and confined modes are found. The results are explained in terms of the light common anion of the compounds. |
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