Electronic structure of phosphorus and arsenic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>δ</mml:mi></mml:math>-doped germanium

Carter, Damien; Warschkow, Oliver; Gale, Julian D.; Scappucci, Giordano; Klesse, Wolfgang M.; Capellini, Giovanni; Rohl, Andrew L.; Simmons, M. Y.; McKenzie, David R.; Marks, Nigel A.

doi:10.1103/physrevb.88.115203

Cited by 4 publications

(11 citation statements)

References 38 publications

(30 reference statements)

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“…The critical role of the interlayer spacing d on the electronic transition from 2D to 3D behaviour is further explored using density functional theory in which the activated dopant densities are used as input parameters. A single phosphorus layer in germanium 24 is characterized by a pair of valley-split bands ( Fig. 3a , labelled 1L′ and 2L′), and a 2DEG density that is spatially confined to a width of ≈7.3 nm by the self-consistent doping potential ( Fig.…”

Section: Discussionmentioning

confidence: 99%

“…DFT calculations on stacked phosphorus dopant layers in germanium were conducted using the SIESTA software 28 and methods described for single Ge:P layers in Ref. 24 . The DFT equations were solved using an atom-centered, double-numerical-plus-polarization (DNP) basis set and the local density approximation (LDA) with empirical on-site (+U) correction.…”

Section: Methodsmentioning

confidence: 99%

“…Phosphorus densities of 6.3 × 10 13 cm −2 and 3.1 × 10 13 cm −2 in the dopant plane were represented using the mixed-atom approach described in Ref. 24 . All dopant atoms in the calculations are confined to a single atomic plane.…”

Section: Methodsmentioning

confidence: 99%

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Bottom-up assembly of metallic germanium

Scappucci

Klesse

Yeoh

et al. 2015

Sci Rep

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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 (1019 to 1020 cm−3) low-resistivity (10−4Ω · 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.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Bottom-up assembly of metallic germanium

Scappucci

Klesse

Yeoh

et al. 2015

Sci Rep

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“…Approaches based on first-principles methods with atomic pseudopotentials and the super-cell model have up to now been very demanding from a computational point of view because satisfactory accuracies can only be achieved using tens of thousands of atoms in the super-cell. The most successful applications of first-principles methods have been carried out for delta-doped layers [10], delta-doped wires [11] and a single impurity in silicon [12]. In the latter case, a satisfactory accuracy has been achieved for a super-cell consisting of 10 648 atoms [12].…”

Section: Introductionmentioning

confidence: 99%

Electronic states and wavefunctions of diatomic donor molecular ions in silicon: multi-valley envelope function theory

Klymenko

Remacle

2014

J. Phys.: Condens. Matter

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Using the Burt-Foreman envelope function theory and effective mass approximation, we develop a theoretical model for an arbitrary number of interacting donor atoms embedded in silicon which reproduces the electronic energy spectrum with high computational efficiency, taking into account the effective mass anisotropy and the valley-orbit coupling. We show that the variation of the relative magnitudes of the electronic coupling between the donor atoms with respect to the valley-orbit coupling as a function of the internuclear distance leads to different kinds of spatial interference patterns of the wavefunction. We also report on the impact of the orientation of the diatomic phosphorus donor molecular ion in the crystal lattice on the ionization energy and on the energy separation between the ground state and the lowest excited state.

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“…30,42 Thickness-Dependent Energy Splitting. To understand the Dirac cone splitting, useful comparisons may be drawn with the valley splitting of quantum well states hosted by semiconductors such as Si, 31,32 Ge, 33 and AlSb. 34 The effective mass approximation (EMA) is a useful framework here.…”

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confidence: 99%

Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures

et al. 2017

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The 'double Dirac cone' 2D topological interface states found on the (001) faces of topological crystalline insulators such as Pb1−xSnxSe feature degeneracies located away from time reversal invariant momenta, and are a manifestation of both mirror symmetry protection and valley interactions. Similar shifted degeneracies in 1D interface states have been highlighted as a potential basis for a topological transistor, but realizing such a device will require a detailed understanding of the intervalley physics involved. In addition, the operation of this or similar devices outside of ultra-high vacuum will require encapsulation, and the consequences of this for the topological interface state must be understood. Here we address both topics for the case of 2D surface states using angle-resolved photoemission spectroscopy. We examine bulk Pb1−xSnxSe(001) crystals overgrown with PbSe, realizing trivial/topological heterostructures. We demonstrate that the valley interaction that splits the two Dirac cones at eachX is extremely sensitive to atomic-scale details of the surface, exhibiting non-monotonic changes as PbSe deposition proceeds. This includes an apparent total collapse of the splitting for sub-monolayer coverage, eliminating the Lifshitz transition. For a large overlayer thickness we observe quantized PbSe states, possibly reflecting a symmetry confinement mechanism at the buried topological interface.The recent experimental realization of three dimensional topological insulators has triggered an expansive program of research, driven largely by the accessibility and rich physics of the 2D electronic states hosted on their surfaces. 1-5 These states are often said to be protected, referencing two distinct concepts. Firstly, the electrical connection of a band-inverted and normal material is not possible without the existence of interface states that thread the bulk bandgap. Secondly, in many band-inverted materials some kind of symmetry exists that forbids hybridization between these cross-gap interface states, thereby ensuring that they remain metallic. These basic characteristics of topological interface states are dictated solely by considerations of symmetry and bulk bandstructure, and in the sense that these are not easily affected by perturbations at the surface, can be considered robust.However it does not follow that the interface states are immune to surface perturbations. For example, adsorption of non-magnetic impurities on the topological insulator Bi 2 Se 3 surface can dope the surface states. [6][7][8] Similarly, the topological crystalline insulator (TCI) Pb 1−x Sn x Se can be surface doped with Rb or Sn, 9,10 while lattice distortions that disrupt mirror symmetry open a bandgap. 11,12 For both classes of materials, the surface termination is predicted to play an important role in the topological band dispersions. [13][14][15][16] Details of the interface are also important in special cases where two bulk band inversions project to the same point in the surface Brillouin zone (Fig.1a), i.e...

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Electronic structure of phosphorus and arsenicδ-doped germanium

Cited by 4 publications

References 38 publications

Bottom-up assembly of metallic germanium

Bottom-up assembly of metallic germanium

Electronic states and wavefunctions of diatomic donor molecular ions in silicon: multi-valley envelope function theory

Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures

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