title: Photodetection in Hybrid Single-Layer Graphene/Fully Coherent Germanium Island Nanostructures Selectively Grown on Silicon Nanotip Patterns.
abstract: Dislocation networks are one of the most principle sources deteriorating the performances of devices based on lattice-mismatched heteroepitaxial systems. We demonstrate here a technique enabling fully coherent germanium (Ge) islands selectively grown on nanotip-patterned Si(001) substrates. The silicon (Si)-tip-patterned substrate, fabricated by complementary metal oxide semiconductor compatible nanotechnology, features ∼50-nm-wide Si areas emerging from a SiO2 matrix and arranged in an ordered lattice. Molecular beam epitaxy growths result in Ge nanoislands with high selectivity and having homogeneous shape and size. The ∼850 °C growth temperature required for ensuring selective growth has been shown to lead to the formation of Ge islands of high crystalline quality without extensive Si intermixing (with 91 atom % Ge). Nanotip-patterned wafers result in geometric, kinetic-diffusion-barrier intermixing hindrance, confining the major intermixing to the pedestal region of Ge islands, where kinetic diffusion barriers are, however, high. Theoretical calculations suggest that the thin Si/Ge layer at the interface plays, nevertheless, a significant role in realizing our fully coherent Ge nanoislands free from extended defects especially dislocations. Single-layer graphene/Ge/Si-tip Schottky junctions were fabricated, and thanks to the absence of extended defects in Ge islands, they demonstrate high-performance photodetection characteristics with responsivity of ∼45 mA W(-1) and an Ion/Ioff ratio of ∼10(3).
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.|Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University , Xi'an 710049, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Niu
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.|Dipartimento di Scienze, Università Roma Tre , Viale Marconi 446, 00146 Rome, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Capellini
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Lupina
authors.affiliation: Technische Universität Berlin, Institut für Optik und Atomare Physik , Straße des 17 Juni 135, 10623 Berlin, Germany.
authors.forename: Tore
authors.initials: T
authors.lastname: Niermann
authors.affiliation: L-NESS and Department of Materials Science, Università degli Studi di Milano-Bicocca , via Cozzi 55, I-20125 Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Salvalaglio
authors.affiliation: L-NESS and Department of Materials Science, Università degli Studi di Milano-Bicocca , via Cozzi 55, I-20125 Milan, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Marzegalli
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.
authors.forename: Markus Andreas
authors.initials: MA
authors.lastname: Schubert
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Zaumseil
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.
authors.forename: Hans-Michael
authors.initials: HM
authors.lastname: Krause
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Skibitzki
authors.affiliation: Technische Universität Berlin, Institut für Optik und Atomare Physik , Straße des 17 Juni 135, 10623 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Lehmann
authors.affiliation: L-NESS and Department of Materials Science, Università degli Studi di Milano-Bicocca , via Cozzi 55, I-20125 Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Montalenti
authors.affiliation: Department of Materials Science and Engineering, University of California at Los Angeles , Los Angeles, California 90095-1595, United States.
authors.forename: Ya-Hong
authors.initials: YH
authors.lastname: Xie
authors.affiliation: IHP , Im Technologiepark 25, 15236 Frankfurt (Oder), Germany.|BTU Cottbus-Senftenberg , Konrad-Zuse-Straße 1, 03046 Cottbus, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schroeder
keywords: elastic relaxation; germanium; graphene; photodetection; selective epitaxy