title: Structural investigations of the α12Si-Ge superstructure.
abstract: This article reports the X-ray diffraction-based structural characterization of the α12multilayer structure SiGe2Si2Ge2SiGe12[d'Avezac, Luo, Chanier & Zunger (2012 ▶).Phys. Rev. Lett.108, 027401], which is predicted to form a direct bandgap material. In particular, structural parameters of the superlattice such as thickness and composition as well as interface properties, are obtained. Moreover, it is found that Ge subsequently segregates into layers. These findings are used as input parameters for band structure calculations. It is shown that the direct bandgap properties depend very sensitively on deviations from the nominal structure, and only almost perfect structures can actually yield a direct bandgap. Photoluminescence emission possibly stemming from the superlattice structure is observed.
authors.affiliation: Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria.
authors.forename: Tanja
authors.initials: T
authors.lastname: Etzelstorfer
authors.affiliation: Zentrum für Oberflächen- und Nanoanalytik, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Ahmadpor Monazam
authors.affiliation: L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, via Anzani 42, I-22100 Como, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cecchi
authors.affiliation: Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria ; Charles University, Department of Condensed Matter Physics, Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic.
authors.forename: Dominik
authors.initials: D
authors.lastname: Kriegner
authors.affiliation: L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, via Anzani 42, I-22100 Como, Italy.
authors.forename: Daniel
authors.initials: D
authors.lastname: Chrastina
authors.affiliation: L-NESS and Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, via Roberto Cozzi 55, I-20125 Milano, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Gatti
authors.affiliation: L-NESS and Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, via Roberto Cozzi 55, I-20125 Milano, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Grilli
authors.affiliation: Philipps-Universität Marburg, Fachbereich Physik, AG Experimentelle Halbleiterphysik, Renthof 5, D-35032 Marburg, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Rosemann
authors.affiliation: Philipps-Universität Marburg, Fachbereich Physik, AG Experimentelle Halbleiterphysik, Renthof 5, D-35032 Marburg, Germany.
authors.forename: Sangam
authors.initials: S
authors.lastname: Chatterjee
authors.affiliation: Charles University, Department of Condensed Matter Physics, Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic.
authors.forename: Vaclav
authors.initials: V
authors.lastname: Holý
authors.affiliation: L-NESS and Dipartimento di Scienza dei Materiali, Universitá degli Studi di Milano-Bicocca, via Roberto Cozzi 55, I-20125 Milano, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Pezzoli
authors.affiliation: L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, via Anzani 42, I-22100 Como, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Isella
authors.affiliation: Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria.
authors.forename: Julian
authors.initials: J
authors.lastname: Stangl
keywords: X-ray diffraction; direct bandgap materials; silicon wafers; superlattice structure