The influence of a Si cap on self-organized SiGe islands and the underlying wetting layer

Journal Article · Wed Jun 15 00:00:00 EDT 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3594693· OSTI ID:21538435

Brehm, M; Grydlik, M; Groiss, H; Hackl, F; Schaeffler, F; Fromherz, T; Bauer, G ^[1]

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1. Institut fuer Halbleiter -u. Festkoerperphysik, Universitaet Linz, A-4040 Linz (Austria)

For the prototypical SiGe/Si(001) Stranski-Krastanow (SK) growth system, the influence of intermixing caused by the deposition of a Si cap layer at temperatures T{sub cap} between 300 deg. C and 700 deg. C is studied both for the SiGe wetting layer (WL) and the SiGe islands. Systematic growth experiments were carried out with an ultrahigh resolution of down to 0.005 monolayers (ML) of deposited Ge. The properties of the samples were investigated via photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy. We studied in detail the influence of T{sub cap} in the three main coverage regions of SiGe SK growth, which are (i) the WL build-up regime, (ii) the island nucleation regime, where most of the Ge is supplied via material transfer from the WL, and (iii) the saturation regime, where the WL thickness remains initially stable. At T{sub cap} = 300 deg. C, we found that both the WL and the island are essentially preserved in composition and shape, whereas at 500 deg. C the WL becomes heavily alloyed during capping, and at 700 deg. C the islands also become alloyed. At T{sub cap} = 500 deg. C we found enhanced WL intermixing in the presence of dome-shaped islands, whereas at T{sub cap} 700 deg. C the WL properties become dominated by the dissolution of pyramid-shaped islands upon capping. At Ge coverages above {approx_equal}6 ML, we found an unexpected thickening of the WL, almost independently of T{sub cap}. This finding suggests that the density and the volume of the dome-shaped islands have an upper limit, beyond which excess Ge from the external source again becomes incorporated into the WL. Finally, we compared PL spectra with AFM-based evaluations of the integral island volumes in order to determine in a straightforward manner the average composition of the SiGe islands.

• OSTI ID: 21538435
• Journal Information: Journal of Applied Physics, Vol. 109, Issue 12; Other Information: DOI: 10.1063/1.3594693; (c) 2011 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOMIC FORCE MICROSCOPY
EPITAXY
GERMANIUM ALLOYS
GERMANIUM SILICIDES
INTERACTIONS
LAYERS
MOLECULAR STRUCTURE
PHOTOLUMINESCENCE
QUANTUM DOTS
SATURATION
SEMICONDUCTOR MATERIALS
SILICON ALLOYS
SPECTRA
SPECTROMETERS
SPECTROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
ALLOYS
CRYSTAL GROWTH METHODS
ELECTRON MICROSCOPY
EMISSION
GERMANIUM COMPOUNDS
LUMINESCENCE
MATERIALS
MEASURING INSTRUMENTS
MICROSCOPY
NANOSTRUCTURES
PHOTON EMISSION
SILICIDES
SILICON COMPOUNDS