Excitation Intensity Driven PL Shifts of SiGe Islands on Patterned and Planar Si(001) Substrates: Evidence for Ge-rich Dots in Islands

• Published in: Nanoscale research letters Vol. 5; no. 12; pp. 1868 - 1872
• Main Authors: Brehm, M, Grydlik, M, Hackl, F, Lausecker, E, Fromherz, T, Bauer, G
• Format: Journal Article
• Language: English
• Published: New York Springer New York 01-12-2010; Springer Nature B.V; Springer
• Subjects: 8th International Workshop on Epitaxial Semiconductors on Patterned Substrates and Novel Index Surfaces; Chemistry and Materials Science; Materials Science; Molecular Medicine; Nanochemistry; Nanoscale Science and Technology; Nanotechnology; Nanotechnology and Microengineering; Special Issue; Special Issue Article; AFM; SiGe; Lateral ordering; Island; Intermixing; Photoluminescence
• ISSN: 1931-7573; 1556-276X
• DOI: 10.1007/s11671-010-9713-z

For randomly nucleated SiGe/Si(001) islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber. We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra. The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments.