We review recent progress in the growth and characterization of Si1-xGex islands and Ge dots on (001) Si. We discuss the evolution of the island morphology with Si1-xGex coverage, and the effect of growth parameters or post-growth annealing on the shape of the islands and dots. We outline some of the structural, and optical properties of Si1-xGex islands and review recent progress in the determination of their composition and strain distribution. We describe the use of undulated Si1-xGex islands superlattices for infrared detection at telecommunication wavelengths. We discuss various approaches currently being investigated to engineer Si1-xGex quantum dots and in particular control their size, density and spatial distribution. For example, we show how C pre-deposition on Si (001) can influence nucleation and growth of Ge islands. We also show how low temperature Si homoepitaxy can lead to a particular surface cusp morphology that may promote dot nucleation.
We report on the development of building blocks of Si/Si1- xGex/Si planar waveguide WDM circuits -- an optical splitter/combiner and the first demonstration of an Si/Si1- xGex/Si arrayed waveguide grating (AWG) demultiplexer. The prototype AWG is a four channel device with a 400 GHz ((Delta) (lambda) equals 2.3 nm) channel spacing, and operates in the 1300 nm wavelength range. Strain and refractive index in the Si1-xGex epilayers play a critical role in device performance. The AWG waveguide heterostructure has total Si1-xGex layer thickness well beyond the measured critical thickness for lattice relaxation, but is stabilized against dislocation formation by the insertion of Si capping layers during growth. Single mode curved ridge waveguides formed from this material show no obvious bend losses for radii of curvature as small as 4 mm.
Nanocrystalline (nc)-Si/amorphous (a)-SiO2 superlattices (SLs) have been studied by transmission electron microscopy, Auger elemental microanalysis (AEM), Raman spectroscopy and optical reflection spectroscopy. Recrystallized Si/SiO2 SL is extremely stable under high temperature annealing (up to 1100 degree(s)C) and aggressive wet thermal oxidation: AEM and Raman spectroscopy of folded acoustic phonons show no changes in periodicity in the growth direction and the abruptness of the nc-Si/a-SiO2 interfaces. Furthermore, Raman spectroscopy in the optical phonon range indicates that the annealing decreases the defect density in the Si nanocrystals, possibly due to Si-Si bond rearrangement accompanied by surface reconstruction and surface defect passivation by oxygen.
Dan-Xia Xu, Siegfried Janz, Robin Williams, Elizabeth Allegretto, Sylvain Mailhot, Jian Jun He, Jean-Marc Baribeau, Hugues Lafontaine, John Stapledon, Jeffrey Fraser, Mike Robillard, Paul Jessop, Stephen Kovacic
The design of manufacturable Si/Si1-xGex waveguide WDM components involves several unique materials and fabrication issues which must be confronted and resolved. Accurate data for the refractive indices of the waveguide materials are essential. Furthermore, the waveguide design is tightly constrained by the requirement that Si/Si1-xGex layer thickness is within the pseudomorphic growth limit. By combining refractive indices determined from mode profile measurements of MBE and CVD grown waveguides, and epilayer thickness constraints set by the pseudomorphic growth limits, we have determined a set of design criteria for Si/Si1-xGex waveguides for WDM and optical signal routing applications. Optically smooth and vertical Si/Si1-xGex waveguide facets are critical in permitting highly efficient coupling between the fiber and the Si chip. Since Si has an equal probability of cleaving alone either the <110> or <111> planes, producing such high quality facets consistently is extremely challenging. We have demonstrated that high quality facets can be obtained consistently by cleaving, with and without a dielectric layer on Si substrates.
Optical transitions in the range I .9—4.3eV have been observed in Si:Ge superlattices by spectroscopic ellipsometry (SE) and electron—beam electroreflectance (EBER). Interference is shown to play an important role in both techniques, leading to complications in • interpretation. Strong features may be produced both by multiple reflections from capping layers and from buried growth imperfections.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.