title: Bottom-up assembly of metallic germanium.
abstract: Extending chip performance beyond current limits of miniaturisation requires new materials and functionalities that integrate well with the silicon platform. Germanium fits these requirements and has been proposed as a high-mobility channel material, a light emitting medium in silicon-integrated lasers, and a plasmonic conductor for bio-sensing. Common to these diverse applications is the need for homogeneous, high electron densities in three-dimensions (3D). Here we use a bottom-up approach to demonstrate the 3D assembly of atomically sharp doping profiles in germanium by a repeated stacking of two-dimensional (2D) high-density phosphorus layers. This produces high-density (10(19) to 10(20) cm(-3)) low-resistivity (10(-4)Ω · cm) metallic germanium of precisely defined thickness, beyond the capabilities of diffusion-based doping technologies. We demonstrate that free electrons from distinct 2D dopant layers coalesce into a homogeneous 3D conductor using anisotropic quantum interference measurements, atom probe tomography, and density functional theory.
authors.affiliation: School of Physics, University of New South Wales, Sydney, 2052, Australia.
authors.forename: Giordano
authors.initials: G
authors.lastname: Scappucci
authors.affiliation: School of Physics, University of New South Wales, Sydney, 2052, Australia.
authors.forename: Wolfgang M
authors.initials: WM
authors.lastname: Klesse
authors.affiliation: School of Physics, University of New South Wales, Sydney, 2052, Australia.
authors.forename: LaReine A
authors.initials: LA
authors.lastname: Yeoh
authors.affiliation: 1] Department of Chemistry, Curtin University, Perth WA 6845, Australia. [2] Nanochemistry Research Institute, Curtin University, Perth WA 6845, Australia.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Carter
authors.affiliation: Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney NSW 2006, Australia.
authors.forename: Oliver
authors.initials: O
authors.lastname: Warschkow
authors.affiliation: 1] Nanochemistry Research Institute, Curtin University, Perth WA 6845, Australia. [2] Department of Physics and Astronomy, Curtin University, Perth WA 6845, Australia.
authors.forename: Nigel A
authors.initials: NA
authors.lastname: Marks
authors.affiliation: Department of Material Science and Engineering, University of North Texas, Denton, Texas 76209, United States.
authors.forename: David L
authors.initials: DL
authors.lastname: Jaeger
authors.affiliation: 1] IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany. [2] Dipartimento di Scienze, Università Roma Tre, Viale Marconi 446, 00146 Rome, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Capellini
authors.affiliation: 1] School of Physics, University of New South Wales, Sydney, 2052, Australia. [2] Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: Michelle Y
authors.initials: MY
authors.lastname: Simmons
authors.affiliation: School of Physics, University of New South Wales, Sydney, 2052, Australia.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Hamilton