Optical and acoustic phonon modes in self-organized Ge quantum dot superlattices

Raman scattering measurements were carried out in self-organized Ge quantum dot superlattices. The samples consisted of 25 periods of Ge quantum dots with different dot sizes sandwiched by 20 nm Si spacers, and were grown usi ng solid-source molecular-beam epitaxy. Optical phonon modes were found to be around 300 cm(-1), and a dependence of the Raman peak frequency on the s ize of dots was evidenced in good agreement with a prediction based on phon on confinement and strain effects. Acoustic phonons related to the Ge quant um dots have also been observed. (C) 2000 American Institute of Physics. [S 0003-6951(00)03305-2].