Ultradense phosphorus in germanium delta-doped layers

Scappucci, Giordano; Capellini, Giovanni; Lee, Wct; Simmons, M. Y.

doi:10.1063/1.3123391

Cited by 48 publications

(64 citation statements)

References 11 publications

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“…Second is the possibility of creating three dimensional systems starting from a suitable large band gap trivial insulator. The idea then is to place "impurity atoms", again with suitable orbitals and "friendly" chemistry with the host, not unlike the process of δ-doping of phosphorus in silicon [44]. The hybridization of the impurity orbitals would again produce a topological insulating state in the impurity bands under favorable conditions.…”

Section: Two Dimensional Systemsmentioning

confidence: 99%

Topological Insulators in Amorphous Systems

2017

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Our understanding of topological insulators is based on an underlying crystalline lattice where the local electronic degrees of freedom at different sites hybridize with each other in ways that produce nontrivial band topology, and the search for material systems to realize such phases have been strongly influenced by this. Here we theoretically demonstrate topological insulators in systems with a random distribution of sites in space, i. e., a random lattice. This is achieved by constructing hopping models on random lattices whose ground states possess nontrivial topological nature (characterized e. g., by Bott indices) that manifests as quantized conductances in systems with a boundary. By tuning parameters such as the density of sites (for a given range of fermion hopping), we can achieve transitions from trivial to topological phases. We discuss interesting features of these transitions. In two spatial dimensions, we show this for all five symmetry classes (A, AII, D, DIII and C) that are known to host nontrivial topology in crystalline systems. We expect similar physics to be realizable in any dimension and provide an explicit example of a Z2 topological insulator on a random lattice in three spatial dimensions. Our study not only provides a deeper understanding of the topological phases of non-interacting fermions, but also suggests new directions in the pursuit of the laboratory realization of topological quantum matter. Introduction:The band insulating state of many fermions has received renewed attention in recent times [1][2][3]. Clues that the band insulating state may support additional nontrivial physics -attributed to topology -was provided by the discovery of the integer quantum Hall effect[4] and the theoretical work that followed [5][6][7]. These ideas saw a resurgence with the discovery of the two dimensional spin Hall insulator[8-13], soon followed [14][15][16][17] by the three dimensional topological insulator (see [1][2][3]).A complete classification of gapped phases of noninteracting fermions soon appeared [18][19][20][21]. This classification hinges on the ten symmetry classes of Altland and Zirnbauer [22]. In any given spatial dimension d only five symmetry classes of the ten host topologically nontrivial phases (see e.g Kitaev [21]). Two gapped systems are considered to be topologically equivalent if the ground state of one can be reached starting from the ground state of the other by a symmetry preserving adiabatic deformation of the Hamiltonian which does not close the gap during the deformation process. The ground state of a gapped crystalline system is characterized by a set of filled bands. For each point in the Brillouin zone (BZ), this amounts to a Slater determinant state made of Bloch wavefunctions (whose character is determined by the symmetry class) of the filled bands. In d-dimensions this turns out to be a map from the BZ (d-dimensional torus) to points on a symmetric space whose character is determined by the total number of bands and the symmetry of the system [21]. Whethe...

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Section: Two Dimensional Systemsmentioning

confidence: 99%

Topological Insulators in Amorphous Systems

2017

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“…Carrying on from the success of the δ-doped Si:P fabrication route, δ-doped P in Ge (Ge:P) structures are now being fabricated on the nanometre scale utilising the same in situ doping techniques. 53,54 Presently, experiments are focused on highly doped Ge:P δ-layers [54][55][56] which could serve as the channel material in the next generation of high-speed nano-transistors.…”

Section: Application Of the Model To A Ge:p δ-Layermentioning

confidence: 99%

Electronic properties ofδ-doped Si:P and Ge:P layers in the high-density limit using a Thomas-Fermi method

2014

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The Thomas-Fermi-Dirac (TFD) approximation and an sp 3 d 5 s * tight binding method were used to calculate the electronic properties of a δ-doped phosphorus layer in silicon. This self-consistent model improves on the computational efficiency of "more rigorous" empirical tight binding and ab initio density functional theory models without sacrificing the accuracy of these methods. The computational efficiency of the TFD model provides improved scalability for large multi-atom simulations, such as of nanoelectronic devices that have experimental interest. We also present the first theoretically calculated electronic properties of a δ-doped phosphorus layer in germanium as an application of this TFD model.

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“…The electrical properties of the Mn 5 Ge 3 C x /Ge(111) Schottky contacts have been investigated in previous works giving a Schottky barrier (SB) height between 0.30 and 0.56 40 eV [10,11]. The value of the SB width can be tuned in order to reduce Fermi level pinning at the interface by creating an ultrashallow and ultranarrow high doped layer at the vicinity of the Mn 5 Ge 3 C x /Ge(111) interface [12,13]. Thus the growth process of the Mn 5 Ge 3 C x on the Ge(111) should preserve the ultrashallow layer.…”

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confidence: 99%

Very low-temperature epitaxial growth of Mn5Ge3 and Mn5Ge3C0.2 films on Ge(111) using molecular beam epitaxy

et al. 2015

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of the spin injection. To avoid these two phenomena we investigate the growth of Mn 5 Ge 3 and C-doped Mn 5 Ge 3 films on Ge(111) substrates by molecular beam epitaxy at room-temperature. The reactive deposition epitaxy method is used to deposit these films. Reflection high energy electron diffraction, X-ray diffraction analysis, transmission electron microscopy and atomic force microscopy indicate that the crystalline quality is very high. Magnetic characterizations by superconducting quantum interference device and ferromagnetic resonance reinforce the structural analysis results on the thin films quality.

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Ultradense phosphorus in germanium delta-doped layers

Cited by 48 publications

References 11 publications

Topological Insulators in Amorphous Systems

Topological Insulators in Amorphous Systems

Electronic properties ofδ-doped Si:P and Ge:P layers in the high-density limit using a Thomas-Fermi method

Very low-temperature epitaxial growth of Mn5Ge3 and Mn5Ge3C0.2 films on Ge(111) using molecular beam epitaxy

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