title: Correlation of Bandgap Reduction with Inversion Response in (Si)GeSn/High-k/Metal Stacks.
abstract: The bandgap tunability of (Si)GeSn group IV semiconductors opens a new era in Si-technology. Depending on the Si/Sn contents, direct and indirect bandgaps in the range of 0.4-0.8 eV can be obtained, offering a broad spectrum of both photonic and low power electronic applications. In this work, we systematically studied capacitance-voltage characteristics of high-k/metal gate stacks formed on GeSn and SiGeSn alloys with Sn-contents ranging from 0 to 14 at. % and Si-contents from 0 to 10 at. % particularly focusing on the minority carrier inversion response. A clear correlation between the Sn-induced shrinkage of the bandgap energy and enhanced minority carrier response was confirmed using temperature and frequency dependent capacitance voltage-measurements, in good agreement with k.p theory predictions and photoluminescence measurements of the analyzed epilayers as reported earlier. The enhanced minority generation rate for higher Sn-contents can be firmly linked to the bandgap reduction in the GeSn epilayer without significant influence of substrate/interface effects. It thus offers a unique possibility to analyze intrinsic defects in (Si)GeSn epilayers. The extracted dominant defect level for minority carrier inversion lies approximately 0.4 eV above the valence band edge in the studied Sn-content range (0-12.5 at. %). This finding is of critical importance since it shows that the presence of Sn by itself does not impair the minority carrier lifetime. Therefore, the continuous improvement of (Si)GeSn material quality should yield longer nonradiative recombination times which are required for the fabrication of efficient light detectors and to obtain room temperature lasing action.
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: C
authors.identifier: http://orcid.org/0000-0003-1429-4604
authors.initials: C
authors.lastname: Schulte-Braucks
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Narimani
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Glass
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: N
authors.identifier: http://orcid.org/0000-0003-0169-6110
authors.initials: N
authors.lastname: von den Driesch
authors.affiliation: Université Grenoble Alpes , 38000 Grenoble, France.|CEA , LETI, Minatec Campus, 38054 Grenoble, France.
authors.forename: J M
authors.initials: JM
authors.lastname: Hartmann
authors.affiliation: Institute of Microwaves and Photonics, Schools of Electronic and Electrical Engineering, University of Leeds , Leeds L2 9JT, United Kingdom.
authors.forename: Z
authors.initials: Z
authors.lastname: Ikonic
authors.affiliation: Semiconductor Physics Laboratory, KU Leuven , 3001 Leuven, Belgium.
authors.forename: V V
authors.initials: VV
authors.lastname: Afanas'ev
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: Q T
authors.initials: QT
authors.lastname: Zhao
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Mantl
authors.affiliation: Peter Grünberg Institute 9 (PGI 9) and JARA-FIT, Forschungszentrum Juelich GmbH , 52425 Juelich, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Buca
keywords: GeSn; defects; direct band gap; generation/recombination; high-k/metal gate