Depth profile of strain and composition in Si/Ge dot multilayers by microscopic phonon Raman spectroscopy

Journal Article · Thu Dec 01 04:00:00 EST 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2140078· OSTI ID:20714149

Tan, P H; Bougeard, D; Abstreiter, G; Brunner, K ^[1]

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1. Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany)

We characterized strain and Ge content depending on depth in a self-assembled Si/Ge dot multilayer by scanning a microscopic Raman probe at a (110) cleavage plane. The multilayer structure was deposited by molecular-beam epitaxy on a (001) Si substrate and consisted of 80 periods, each of them composed by 25 nm Si spacers and 8 monolayer Ge forming laterally and vertically uncorrelated islands with a height of 2 nm and a lateral diameter of about 20 nm. An average biaxial strain of -3.5% within the core regions of islands is determined from the splitting of longitudinal and transversal optical Ge-Ge phonon modes observed in polarized Raman measurements. The absolute mode frequencies further enable analysis of a Ge content of 0.82. The analyzed strain and composition of islands are nearly independent from depths below the sample surface. This indicates well-controlled deposition parameters and negligible intermixing during deposition of subsequent layers. These Raman results are in agreement with x-ray diffraction data. Small, local Raman frequency shifts were observed and discussed with respect to partial elastic strain relaxation of the multilayer stack after cleavage, undefined Raman-scattering geometries at the sample edge, and local heating by the laser probe.

• OSTI ID: 20714149
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 11 Vol. 98; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CLEAVAGE
CRYSTAL GROWTH
DEPOSITION
GERMANIUM
HEATING
LASERS
LAYERS
MAGNETIC ISLANDS
MOLECULAR BEAM EPITAXY
PHONONS
QUANTUM DOTS
RAMAN SPECTROSCOPY
SEMICONDUCTOR MATERIALS
SILICON
STRAINS
STRESS RELAXATION
SUBSTRATES
X-RAY DIFFRACTION