Size-Selective Raman Scattering in Self-Assembled Ge/Si Quantum Dot Superlattices
RUSSIAN ACADEMY OF SCIENCES NOVOSIBIRSKINST OF SEMICONDUCTOR PHYSICS
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Self-organised Ge quantum dot QD superlattices having properties of two and zero dimensional structures were investigated by Raman spectroscopy. Longitudinal optical Ge LO and Ge-Si L phonons and folded acoustic LA phonons superimposed with a strong continuous emission were studied under resonant conditions. The measured phonon frequencies of folded LA phonons up to 15th order are in a good agreement with those calculated using the Rytov model. The low frequency continuous emission can be explained in terms ofa breakdown of crystal momentum conservation for resonant Raman processes involving acoustic phonons. A frequency enlargement of continuous emission band and a downward shift of LO Ge phonons with increasing excitation energy 2.54-2.71 eV are attiibuted to electron and phonon size-confinement in the small Ge QDs resonantly contributing to the scattering process.
- Atomic and Molecular Physics and Spectroscopy