Analysis of Strain and Intermixing in Single-Layer Ge/Si Quantum Dots Using Polarized Raman Spectroscopy

The built-in strain and composition of as-grown and Si-capped single layers of Ge/ Si dots grown at various temperatures 460– 800 ° C are studied by a comparative analysis of the Ge-Ge and Si-Ge modes in the polarized Raman spectra of the dots. A pronounced reduction of the strain and Ge content in the dots after deposition of the cap layer at low temperatures is observed, indicating that strain-induced Si diffusion from the cap layer is occurring. For large dots grown at 700– 800 ° C the observations are in agreement with a model of the Ge/ Si dot consisting of a Si-rich boundary region and a Ge-rich core.

[1]  Manuel Cardona,et al.  Pressure dependence of Raman phonons of Ge and 3C-SiC , 1982 .

[2]  H. Osten,et al.  Measurement of stress and relaxation in Si1−xGex layers by Raman line shift and x‐ray diffraction , 1993 .

[3]  F. H. Dacol,et al.  Measurements of alloy composition and strain in thin GexSi1−x layers , 1994 .

[4]  Stefano de Gironcoli,et al.  In-plane Raman scattering of (001)-Si/Ge superlattices: Theory and experiment. , 1994, Physical review. B, Condensed matter.

[5]  P. Milani,et al.  Raman, optical‐absorption, and transmission electron microscopy study of size effects in germanium quantum dots , 1996 .

[6]  A. Sood,et al.  In situ Raman monitoring of ultrathin Ge films , 1998 .

[7]  V. Yam,et al.  Vertically self-organized Ge/Si(001) quantum dots in multilayer structures , 1999 .

[8]  M. Li,et al.  Confinement and electron-phonon interactions of the E-1 exciton in self-organized Ge quantum dots , 1999 .

[9]  X. Jiang,et al.  Study of strain in partially relaxed Ge epilayers on Si(100) substrate , 1999 .

[10]  Kang L. Wang,et al.  Response to “Comment on ‘Raman scattering from a self-organized Ge dot superlattice’ ” [Appl. Phys. Lett. 75, 3572 (1999)] , 1999 .

[11]  Comment on “Raman scattering from a self-organized Ge dot superlattice” [Appl. Phys. Lett. 74, 1863 (1999)] , 1999 .

[12]  Oliver G. Schmidt,et al.  Multiple layers of self-asssembled Ge/Si islands: Photoluminescence, strain fields, material interdiffusion, and island formation , 2000 .

[13]  Katsuyuki Watanabe,et al.  Fabrication of GaAs Quantum Dots by Modified Droplet Epitaxy , 2000 .

[14]  A. Kolobov.  Raman scattering from Ge nanostructures grown on Si substrates: Power and limitations , 2000 .

[15]  O. Schmidt,et al.  Strain and band-edge alignment in single and multiple layers of self-assembled Ge/Si and GeSi/Si islands , 2000 .

[16]  K. Teo,et al.  Effects of hydrostatic pressure on Raman scattering in Ge quantum dots , 2001 .

[17]  V. L. Thanh.  New insight into the kinetics of Stranski-Krastanow growth of Ge on Si(001) , 2001 .

[18]  Oliver G. Schmidt,et al.  Effect of overgrowth on shape, composition, and strain of SiGe islands on Si(001) , 2002 .

[19]  Silke Christiansen,et al.  Composition of self-assembled Ge/si islands in single and multiple layers , 2002 .

[20]  G. Hadjisavvas,et al.  Stress and composition of C-induced Ge dots on Si(100) , 2003 .

[21]  Dominique Bougeard,et al.  Raman characterization of strain and composition in small-sized self-assembled Si/Ge dots , 2003 .

[22]  O. Schmidt,et al.  Effect of overgrowth temperature on shape, strain, and composition of buried Ge islands deduced from x-ray diffraction , 2003 .

[23]  O. Schmidt,et al.  Probing the lateral composition profile of self-assembled islands. , 2003, Physical review letters.

[24]  G. Kar,et al.  Extended wavelength region of self-assembled Ge/Si(001) islands capped with Si at different temperatures , 2003 .

[25]  Phonons in Ge/Si quantum dot structures: influence of growth temperature , 2004 .

[26]  Dominique Bougeard,et al.  Raman scattering of folded acoustic phonons in self-assembled Si/Ge dot superlattices , 2004 .

[27]  A. Baranov,et al.  Polarized Raman spectroscopy of multilayer Ge/Si(001) quantum dot heterostructures , 2004 .

[28]  Lateral motion of SiGe islands driven by surface-mediated alloying. , 2005, Physical review letters.

[29]  T. Metzger,et al.  Influence of growth temperature on interdiffusion in uncapped SiGe-islands on Si(001) determined by anomalous x-ray diffraction and reciprocal space mapping , 2005 .

[30]  S. Kawata,et al.  Highly sensitive strain detection in strained silicon by surface-enhanced Raman spectroscopy , 2005 .