Direct observation of the acoustic gaps in Ge/GexSi1−x superlattices

✍ Scribed by V. Lemos; O. Pilla; M. Montagna

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 85 KB
• Volume: 30
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/(sici)1097-4555(199905)30:5<379::aid-jrs390>3.0.co;2-m

✦ Synopsis

Raman spectra of Ge/Ge x Si 1-x superlattices were measured, probing close to the mini-Brillouin zone edge. The data reveal peculiar features in the low-wavenumber region of the spectra. These features are observed as dips superimposed on broad bands, the latter being related to the scattering of pure longitudinal phonons. The bands are broad owing to the contribution of absorption processes to the Raman scattering. Such processes induce strong intensity in a wide range around the probing wavevector. It was found that the dips can be assigned to the gaps of the dispersion relation, with the aid of models based on the photoelastic theory for longitudinal acoustic phonons in superlattices.