Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 25: Si / Ge
HL 25.4: Vortrag
Samstag, 5. März 2005, 11:30–11:45, TU P-N226
Electronic and optical properties of capped Si and Ge nanocrystallites — •Luis Ramos, Jürgen Furthmüller, and Friedhelm Bechstedt — FSU Jena - IFTO, Max-Wien-Platz 1, D-07743 Jena, Germany
Quantum confinement (QC) in Si and Ge nanocrystallites (NC’s) gives rise to new material properties interesting to applications such as data storage devices, photodetectors, and optoelectronics. The lattice mismatch of Si and Ge and the fact that Si1−xGex is a highly miscible alloy for all concentrations x could prevent very sharp Si/Ge interfaces. However, a considerable progress in controlling the growth of Si/Ge heterostructures has been achieved and novel structures with embedded NC’s can be synthetised.
In this work we present ab-initio pseudopotential plane-wave calculations for Si(Ge)-capped Ge(Si) free-standing NC’s. We study their structural and electronic properties, optical absorption spectra, Stokes shifts, radiative lifetimes, and the space localization of the HOMO and LUMO. We verify that Si-(Ge-)capped Ge(Si) NC’s have significant differences in their structures and the type-II character of a Si/Ge heterojunction. In certain cases the absorption spectra shows a compensation effect related to composition and QC effects. The results are compared to those of Si NC’s capped with oxide shells.