Ge dots and nanostructures grown epitaxially on Si

Abstract

We review recent progress in the growth and characterization of Si 1−x Ge x islands and Ge dots on (001) Si. We discuss the evolution of the island morphology with Si 1−x Ge x coverage, and the effect of growth parameters or post-growth annealing on the shape of islands and dots. We outline some of the structural, vibrational, and optical properties of Si 1−x Ge x islands and review recent advances in the determination of their composition and strain distribution. In particular, we present an analytical electron transmission microscopy study of the Ge spatial distribution in Ge dots and Si/Si 1−x Ge x island superlattices grown by molecular beam epitaxy and ultra-high vacuum chemical vapour deposition. We describe the use of undulated Si 1−x Ge x island superlattices for infrared detection at telecommunication wavelengths. Finally, we discuss various approaches currently being investigated to engineer Si 1−x Ge x quantum dots and, in particular, control their size, density, and spatial distribution. As examples, we show how C pre-deposition on Si(001) can influence nucleation and growth of Ge islands and how low temperature Si homo-epitaxy can lead to a particular surface cusp morphology that may promote dot nucleation.

Self‐assembled silicon‐germanium nanostructures for CMOS compatible light emitters

“…Thus, systematic studies of the PL spectra in 3D Si/Si 1-x Ge x NSs with control over the average Ge atomic concentration x provide very important information regarding changes in the carrier recombination mechanism (e.g., selection rule relaxation, conduction and valence band alignment, etc.) as x increases from 0 (bulk Si) to ~55%, which is the highest Ge composition in structurally defect-free SiGe clusters [5].…”

“…PL measurements in Si/SiGe NSs reveal a significantly enhanced intensity ratio between no-phonon (NP) luminescence and phononassisted luminescence compared to bulk Si [5]. Thus, systematic studies of the PL spectra in 3D Si/Si 1-x Ge x NSs with control over the average Ge atomic concentration x provide very important information regarding changes in the carrier recombination mechanism (e.g., selection rule relaxation, conduction and valence band alignment, etc.)…”

“…In contrast to MBE grown samples, chemical vapour deposition (CVD) growth of 3D Si/SiGe NSs does not provide precise control over the atomic composition, and can produce more Si/SiGe interdiffusion at heterointerfaces [5]. This is reflected in PL spectra, where no fine structure has been found.…”

“…By the 1990s, a different form of SiGe NS, namely the three-dimensional (3D) self-assembled system produced by the Stranski-Krastanov growth mode in lattice mismatched materials, had been demonstrated [5]. It has been shown that dislocation-free SiGe growth can be achieved using a higher temperature (≥600 o C), and that the non-planar geometry is mainly responsible for the significant increase of the SiGe critical layer thickness [5].…”

“…It has been shown that dislocation-free SiGe growth can be achieved using a higher temperature (≥600 o C), and that the non-planar geometry is mainly responsible for the significant increase of the SiGe critical layer thickness [5]. It has also been found that, compared to two-dimemensional (2D) Si/SiGe NSs, the PL and electroluminescence (EL) quantum efficiency in 3D Si/SiGe NSs is higher (up to ~1%), especially for T > 50 K [6][7][8][9].…”