Abstract
A dramatically enhanced self-assembly of GeSi quantum dots (QDs) is disclosed on slightly miscut Si (001) substrates, leading to extremely dense QDs and even a growth mode transition. The inherent mechanism is addressed in combination of the thermodynamics and the growth kinetics both affected by steps on the vicinal surface. Moreover, temperature-dependent photoluminescence spectra from dense GeSi QDs on the miscut substrate demonstrate a rather strong peak persistent up to 300 K, which is attributed to the well confinement of excitons in the dense GeSi QDs due to the absence of the wetting layer on the miscut substrate.
Highlights
Self-assembled GeSi quantum dots (QDs) on Si substrates have attracted broad attentions both for their potential applications in devices[1,2,3] compatible with the sophisticated Si technology and to understand the fundamental physics[4,5,6] during the heteroepitaxial growth as a prototype model
The different shape of the GeSi QDs on miscut Si (001) substrates are naturally formed since the energetic stability of facets, e.g., {1, 0, 5} facets, is essentially not affected by the steps on slightly miscut substrates
By slightly changing the miscut angle, a significant increase of QD density by more than two orders of magnitude is realized, and a transition from Stranski-Krastanov (SK) to Volmer-Weber (VW) growth mode can occur. Such unique features of self-assembled QDs on miscut substrates have never been expected in Ge/Si system due to its quite small lattice mismatch of less than 4.2%. These novel phenomena are explained from the point views of the energetics and the growth kinetics during the QDs formation, which are both affected by steps on the miscut substrates
Summary
Self-assembled GeSi quantum dots (QDs) on Si substrates have attracted broad attentions both for their potential applications in devices[1,2,3] compatible with the sophisticated Si technology and to understand the fundamental physics[4,5,6] during the heteroepitaxial growth as a prototype model. Such a strong PL peak mainly results from the well hole confinement in the dense GeSi QDs without the wetting layer on the miscut substrates.
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