ORCID Profile
0000-0001-7128-773X
Current Organisation
Purdue University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Condensed Matter Physics | Condensed Matter Modelling and Density Functional Theory | Quantum Physics | Quantum Optics | Quantum Information, Computation and Communication | Condensed Matter Physics—Electronic And Magnetic Properties; | Condensed Matter Physics—Structural Properties | Mathematical Physics | Quantum Chemistry | Lasers and Quantum Electronics | Optics And Opto-Electronic Physics
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Physical sciences | Expanding Knowledge in Technology | Environmentally Sustainable Information and Communication Services not elsewhere classified | Education and Training not elsewhere classified | Expanding Knowledge in the Chemical Sciences | Network Infrastructure Equipment | National Security |
Related Links
Publications
Silicon quantum electronics
Publisher: American Physical Society (APS)
Date: 10-07-2013
Thickness Engineered Tunnel Field-Effect Transistors Based on Phosphorene
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2017
Determination of the eigenstates and wavefunctions of a single gated As donor
Publisher: IEEE
Date: 02-2008
Erratum: Lifetime-Enhanced Transport in Silicon due to Spin and Valley Blockade [Phys. Rev. Lett.107, 136602 (2011)]
Publisher: American Physical Society (APS)
Date: 23-01-2013
Electric field reduced charging energies and two-electron bound excited states of single donors in silicon
Publisher: American Physical Society (APS)
Date: 19-09-2011
Atomistic Simulation of Realistically Sized Nanodevices Using NEMO 3-D—Part I: Models and Benchmarks
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2007
Spatially resolving valley quantum interference of a donor in silicon
Publisher: Springer Science and Business Media LLC
Date: 06-04-2014
DOI: 10.1038/NMAT3941
Abstract: Electron and nuclear spins of donor ensembles in isotopically pure silicon experience a vacuum-like environment, giving them extraordinary coherence. However, in contrast to a real vacuum, electrons in silicon occupy quantum superpositions of valleys in momentum space. Addressable single-qubit and two-qubit operations in silicon require that qubits are placed near interfaces, modifying the valley degrees of freedom associated with these quantum superpositions and strongly influencing qubit relaxation and exchange processes. Yet to date, spectroscopic measurements have only probed wavefunctions indirectly, preventing direct experimental access to valley population, donor position and environment. Here we directly probe the probability density of single quantum states of in idual subsurface donors, in real space and reciprocal space, using scanning tunnelling spectroscopy. We directly observe quantum mechanical valley interference patterns associated with linear superpositions of valleys in the donor ground state. The valley population is found to be within 5% of a bulk donor when 2.85 ± 0.45 nm from the interface, indicating that valley-perturbation-induced enhancement of spin relaxation will be negligible for depths greater than 3 nm. The observed valley interference will render two-qubit exchange gates sensitive to atomic-scale variations in positions of subsurface donors. Moreover, these results will also be of interest for emerging schemes proposing to encode information directly in valley polarization.
Sensitivity Challenge of Steep Transistors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2018
Universal Behavior of Atomistic Strain in Self-Assembled Quantum Dots
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2016
Silicon at the fundamental scaling limit-atomic-scale donor-based quantum electronics
Publisher: IEEE
Date: 06-2014
Experimental and theoretical study of polarization-dependent optical transitions in InAs quantum dots at telecommunication-wavelengths (1300-1500 nm)
Publisher: AIP Publishing
Date: 15-05-2011
DOI: 10.1063/1.3587167
Abstract: The design of some optical devices, such as semiconductor optical lifiers for telecommunication applications, requires polarization-insensitive optical emission at long wavelengths (1300–1550 nm). Self-assembled InAs/GaAs quantum dots (QDs) typically exhibit ground state optical emissions at wavelengths shorter than 1300 nm with highly polarization-sensitive characteristics, although this can be modified by the use of low growth rates, the incorporation of strain-reducing capping layers, or the growth of closely-stacked QD layers. Exploiting the strain interactions between closely stacked QD layers also affords greater freedom in the choice of growth conditions for the upper layers, so that both a significant extension in their emission wavelength and an improved polarization response can be achieved due to modification of the QD size, strain, and composition. In this paper, we investigate the polarization behavior of single and stacked QD layers using room temperature sub-lasing-threshold electroluminescence and photovoltage measurements, as well as atomistic modeling with the NEMO 3-D simulator. A reduction is observed in the ratio of the transverse electric (TE) to transverse magnetic (TM) optical mode response for a GaAs-capped QD stack as compared to a single QD layer, but when the second layer of the two-layer stack is InGaAs-capped, an increase in the TE/TM ratio is observed, in contrast to recent reports for single QD layers.
Spin-Lattice Relaxation Times of Single Donors and Donor Clusters in Silicon
Publisher: American Physical Society (APS)
Date: 11-12-2014
Limits to Metallic Conduction in Atomic-Scale Quasi-One-Dimensional Silicon Wires
Publisher: American Physical Society (APS)
Date: 10-12-2014
Coherent Control of a SingleSi
Publisher:
American Physical Society (APS)
Date:
09-12-2014
Publisher: American Physical Society (APS)
Date: 09-12-2014
Genetically engineered nanoelectronics
Publisher: IEEE Comput. Soc
Date: 1999
Design Rules for High Performance Tunnel Transistors From 2-D Materials
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2016
Ohm’s Law Survives to the Atomic Scale
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-01-2012
Abstract: One of the challenges in downsizing electronic circuits is maintaining low resistivity of wires, because shrinking their diameter to near atomic dimensions increases interface effects and can decrease the effectiveness of dopants. Weber et al. (p. 64 see the Perspective by Ferry ) created nanowires on a silicon surface with the deposition of phosphorus atoms through decomposition of PH 3 with a scanning tunneling microscope tip. A brief thermal annealing embedded these nanowires, which varied from 1.5 to 11 nanometers in width, into the silicon surface. Their resistivity was independent of width, and their current-carrying capability was comparable to that of thicker copper interconnects.
Thermionic Emission as a Tool to Study Transport in Undoped nFinFETs
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2010
Tunnel Field-Effect Transistors in 2-D Transition Metal Dichalcogenide Materials
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
Polarization-Engineered III-Nitride Heterojunction Tunnel Field-Effect Transistors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
Atomistic modeling of metallic nanowires in silicon
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3NR01796F
Abstract: Scanning tunneling microscope (STM) lithography has recently demonstrated the ultimate in device scaling with buried, conducting nanowires just a few atoms wide and the realization of single atom transistors, where a single P atom has been placed inside a transistor architecture with atomic precision accuracy. Despite the dimensions of the critical parts of these devices being defined by a small number of P atoms, the device electronic properties are influenced by the surrounding 10(4) to 10(6) Si atoms. Such effects are hard to capture with most modeling approaches, and prior to this work no theory existed that could explore the realistic size of the complete device in which both dopant disorder and placement are important. This work presents a comprehensive study of the electronic and transport properties of ultra-thin (<10 nm wide) monolayer highly P δ-doped Si (Si:P) nanowires in a fully atomistic self-consistent tight-binding approach. This atomistic approach covering large device volumes allows for a systematic study of disorder on the physical properties of the nanowires. Excellent quantitative agreement is observed with recent resistance measurements of STM-patterned nanowires [Weber et al., Science, 2012, 335, 64], confirming the presence of metallic behavior at the scaling limit. At high doping densities the channel resistance is shown to be insensitive to the exact channel dopant placement highlighting their future use as metallic interconnects. This work presents the first theoretical study of Si:P nanowires that are realistically extended and disordered, providing a strong theoretical foundation for the design and understanding of atomic-scale electronics.
Spin blockade and exchange in Coulomb-confined silicon double quantum dots
Publisher: Springer Science and Business Media LLC
Date: 13-04-2014
Abstract: Electron spins confined to phosphorus donors in silicon are promising candidates as qubits because of their long coherence times, exceeding seconds in isotopically purified bulk silicon. With the recent demonstrations of initialization, readout and coherent manipulation of in idual donor electron spins, the next challenge towards the realization of a Si:P donor-based quantum computer is the demonstration of exchange coupling in two tunnel-coupled phosphorus donors. Spin-to-charge conversion via Pauli spin blockade, an essential ingredient for reading out in idual spin states, is challenging in donor-based systems due to the inherently large donor charging energies (∼45 meV), requiring large electric fields (>1 MV m(-1)) to transfer both electron spins onto the same donor. Here, in a carefully characterized double donor-dot device, we directly observe spin blockade of the first few electrons and measure the effective exchange interaction between electron spins in coupled Coulomb-confined systems.
Quantum Confined Stark Shift and Ground State Optical Transition Rate in [100] Laterally Biased InAs/GaAs Quantum Dots
Publisher: IEEE
Date: 05-2009
Eigenvalue solvers for atomistic simulations of electronic structures with NEMO-3D
Publisher: Springer Science and Business Media LLC
Date: 22-02-2008
Symmetry Breaking and Fine Structure Splitting in Zincblende Quantum Dots: Atomistic Simulations of Long-Range Strain and Piezoelectric Field
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2730157
Interface-induced heavy-hole/light-hole splitting of acceptors in silicon
Publisher: AIP Publishing
Date: 18-05-2015
DOI: 10.1063/1.4921640
Abstract: The energy spectrum of spin-orbit coupled states of in idual sub-surface boron acceptor dopants in silicon have been investigated using scanning tunneling spectroscopy at cryogenic temperatures. The spatially resolved tunnel spectra show two resonances, which we ascribe to the heavy- and light-hole Kramers doublets. This type of broken degeneracy has recently been argued to be advantageous for the lifetime of acceptor-based qubits [R. Ruskov and C. Tahan, Phys. Rev. B 88, 064308 (2013)]. The depth dependent energy splitting between the heavy- and light-hole Kramers doublets is consistent with tight binding calculations, and is in excess of 1 meV for all acceptors within the experimentally accessible depth range (& nm from the surface). These results will aid the development of tunable acceptor-based qubits in silicon with long coherence times and the possibility for electrical manipulation.
Electrically doped WTe<inf>2</inf> tunnel transistors
Publisher: IEEE
Date: 09-2015
Quantum simulation of the Hubbard model with dopant atoms in silicon
Publisher: Springer Science and Business Media LLC
Date: 20-04-2016
DOI: 10.1038/NCOMMS11342
Abstract: In quantum simulation, many-body phenomena are probed in controllable quantum systems. Recently, simulation of Bose–Hubbard Hamiltonians using cold atoms revealed previously hidden local correlations. However, fermionic many-body Hubbard phenomena such as unconventional superconductivity and spin liquids are more difficult to simulate using cold atoms. To date the required single-site measurements and cooling remain problematic, while only ensemble measurements have been achieved. Here we simulate a two-site Hubbard Hamiltonian at low effective temperatures with single-site resolution using subsurface dopants in silicon. We measure quasi-particle tunnelling maps of spin-resolved states with atomic resolution, finding interference processes from which the entanglement entropy and Hubbard interactions are quantified. Entanglement, determined by spin and orbital degrees of freedom, increases with increasing valence bond length. We find separation-tunable Hubbard interaction strengths that are suitable for simulating strongly correlated phenomena in larger arrays of dopants, establishing dopants as a platform for quantum simulation of the Hubbard model.
Transport-based dopant metrology in advanced FinFETs
Publisher: IEEE
Date: 12-2008
Designing a large scale quantum computer with atomistic simulations
Publisher: IEEE
Date: 06-2014
Electrically doped 2D material tunnel transistor
Publisher: IEEE
Date: 09-2015
A Tight-Binding Study of Single-Atom Transistors
Publisher: Wiley
Date: 08-10-2014
Abstract: A detailed theoretical study of the electronic and transport properties of a single atom transistor, where a single phosphorus atom is embedded within a single crystal transistor architecture, is presented. Using a recently reported deterministic single-atom transistor as a reference, the electronic structure of the device is represented atomistically with a tight-binding model, and the channel modulation is simulated self-consistently with a Thomas-Fermi method. The multi-scale modeling approach used allows confirmation of the charging energy of the one-electron donor charge state and explains how the electrostatic environments of the device electrodes affects the donor confinement potential and hence extent in gate voltage of the two-electron charge state. Importantly, whilst devices are relatively insensitive to dopant ordering in the highly doped leads, a ∼1% variation of the charging energy is observed when a dopant is moved just one lattice spacing within the device. The multi-scale modeling method presented here lays a strong foundation for the understanding of single-atom device structures: essential for both classical and quantum information processing.
Strain and electronic structure interactions in realistically-scaled quantum dot stacks
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2730156
High Precision Quantum Control of Single Donor Spins in Silicon
Publisher: American Physical Society (APS)
Date: 20-07-2007
Scaling Theory of Electrically Doped 2D Transistors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2015
A Tight Binding Study of Strain-Reduced Confinement Potentials in Identical and Non-Identical InAs/GaAs Vertically Stacked Quantum Dots
Publisher: IEEE
Date: 08-2008
Atomistic simulation of steep subthreshold slope Bi-layer MoS<inf>2</inf> transistors
Publisher: IEEE
Date: 06-2014
+Level Spectrum Of Single Gated As Donors
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3295570
Channel Thickness Optimization for Ultrathin and 2-D Chemically Doped TFETs
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2018
Si tight-binding parameters from genetic algorithm fitting
Publisher: Elsevier BV
Date: 02-2000
Transport of spin qubits with donor chains under realistic experimental conditions
Publisher: American Physical Society (APS)
Date: 25-07-2016
Strain and electric field control of hyperfine interactions for donor spin qubits in silicon
Publisher: American Physical Society (APS)
Date: 25-06-2015
Sub-threshold study of undoped trigate nFinFET
Publisher: Elsevier BV
Date: 02-2010
Moving Toward Nano-TCAD Through Multimillion-Atom Quantum-Dot Simulations Matching Experimental Data
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2009
Quantum transport in ultra-scaled phosphorous-doped silicon nanowires
Publisher: IEEE
Date: 06-2010
Dramatic Impact of Dimensionality on the Electrostatics of P-N Junctions and Its Sensing and Switching Applications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2018
Electrically Tunable Bandgaps in Bilayer MoS2
Publisher: American Chemical Society (ACS)
Date: 13-11-2015
DOI: 10.1021/ACS.NANOLETT.5B03218
Abstract: Artificial semiconductors with manufactured band structures have opened up many new applications in the field of optoelectronics. The emerging two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs), cover a large range of bandgaps and have shown potential in high performance device applications. Interestingly, the ultrathin body and anisotropic material properties of the layered TMDs allow a wide range modification of their band structures by electric field, which is obviously desirable for many nanoelectronic and nanophotonic applications. Here, we demonstrate a continuous bandgap tuning in bilayer MoS2 using a dual-gated field-effect transistor (FET) and photoluminescence (PL) spectroscopy. Density functional theory (DFT) is employed to calculate the field dependent band structures, attributing the widely tunable bandgap to an interlayer direct bandgap transition. This unique electric field controlled spontaneous bandgap modulation approaching the limit of semiconductor-to-metal transition can open up a new field of not yet existing applications.
Publisher’s Note: Engineered valley-orbit splittings in quantum-confined nanostructures in silicon [Phys. Rev. B83, 195323 (2011)]
Publisher: American Physical Society (APS)
Date: 15-06-2011
Switching Mechanism and the Scalability of Vertical-TFETs
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2018
Full-band study of ultra-thin Si:P nanowires
Publisher: IEEE
Date: 05-2012
Gate-inducedg
Publisher: American Physical Society (APS)
Date: 10-2009
Silicon quantum processor with robust long-distance qubit couplings
Publisher: Springer Science and Business Media LLC
Date: 06-09-2017
DOI: 10.1038/S41467-017-00378-X
Abstract: Practical quantum computers require a large network of highly coherent qubits, interconnected in a design robust against errors. Donor spins in silicon provide state-of-the-art coherence and quantum gate fidelities, in a platform adapted from industrial semiconductor processing. Here we present a scalable design for a silicon quantum processor that does not require precise donor placement and leaves le space for the routing of interconnects and readout devices. We introduce the flip-flop qubit, a combination of the electron-nuclear spin states of a phosphorus donor that can be controlled by microwave electric fields. Two-qubit gates exploit a second-order electric dipole-dipole interaction, allowing selective coupling beyond the nearest-neighbor, at separations of hundreds of nanometers, while microwave resonators can extend the entanglement to macroscopic distances. We predict gate fidelities within fault-tolerance thresholds using realistic noise models. This design provides a realizable blueprint for scalable spin-based quantum computers in silicon.
Optimization of the anharmonic strain model to capture realistic strain distributions in quantum dots
Publisher: IEEE
Date: 08-2014
Lifetime-Enhanced Transport in Silicon due to Spin and Valley Blockade
Publisher: American Physical Society (APS)
Date: 19-09-2011
Atomistic Simulation of Realistically Sized Nanodevices Using NEMO 3-D—Part II: Applications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2007
Noninvasive Spatial Metrology of Single-Atom Devices
Publisher: American Chemical Society (ACS)
Date: 18-04-2013
DOI: 10.1021/NL303863S
Abstract: The exact location of a single dopant atom in a nanostructure can influence or fully determine the functionality of highly scaled transistors or spin-based devices. We demonstrate here a noninvasive spatial metrology technique, based on the microscopic modeling of three electrical measurements on a single-atom (phosphorus in silicon) spin qubit device: hyperfine coupling, ground state energy, and capacitive coupling to nearby gates. This technique allows us to locate the qubit atom with a precision of ±2.5 nm in two directions and ±15 nm in the third direction, which represents a 1500-fold improvement with respect to the prefabrication statistics obtainable from the ion implantation parameters.
Experimental and atomistic theoretical study of degree of polarization from multilayer InAs/GaAs quantum dot stacks
Publisher: American Physical Society (APS)
Date: 23-09-2011
Engineered valley-orbit splittings in quantum-confined nanostructures in silicon
Publisher: American Physical Society (APS)
Date: 26-05-2011
Quantitative excited state spectroscopy of a single InGaAs quantum dot molecule through multi-million-atom electronic structure calculations
Publisher: IOP Publishing
Date: 08-07-2011
DOI: 10.1088/0957-4484/22/31/315709
Abstract: Atomistic electronic structure calculations are performed to study the coherent inter-dot couplings of the electronic states in a single InGaAs quantum dot molecule. The experimentally observed excitonic spectrum by Krenner et al (2005) Phys. Rev. Lett. 94 057402 is quantitatively reproduced, and the correct energy states are identified based on a previously validated atomistic tight binding model. The extended devices are represented explicitly in space with 15-million-atom structures. An excited state spectroscopy technique is applied where the externally applied electric field is swept to probe the ladder of the electronic energy levels (electron or hole) of one quantum dot through anti-crossings with the energy levels of the other quantum dot in a two-quantum-dot molecule. This technique can be used to estimate the spatial electron-hole spacing inside the quantum dot molecule as well as to reverse engineer quantum dot geometry parameters such as the quantum dot separation. Crystal-deformation-induced piezoelectric effects have been discussed in the literature as minor perturbations lifting degeneracies of the electron excited (P and D) states, thus affecting polarization alignment of wavefunction lobes for III-V heterostructures such as single InAs/GaAs quantum dots. In contrast, this work demonstrates the crucial importance of piezoelectricity to resolve the symmetries and energies of the excited states through matching the experimentally measured spectrum in an InGaAs quantum dot molecule under the influence of an electric field. Both linear and quadratic piezoelectric effects are studied for the first time for a quantum dot molecule and demonstrated to be indeed important. The net piezoelectric contribution is found to be critical in determining the correct energy spectrum, which is in contrast to recent studies reporting vanishing net piezoelectric contributions.
Transport spectroscopy of a single atom in a FinFET
Publisher: IOP Publishing
Date: 03-2008
Achieving a higher performance in bilayer graphene FET - strain engineering
Publisher: IEEE
Date: 09-2015
Dielectric Engineered Tunnel Field-Effect Transistor
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2015
A predictive analytic model for high-performance tunneling field-effect transistors approaching non-equilibrium Green's function simulations
Publisher: AIP Publishing
Date: 28-10-2015
DOI: 10.1063/1.4934682
Abstract: A new compact modeling approach is presented which describes the full current-voltage (I-V) characteristic of high-performance (aggressively scaled-down) tunneling field-effect-transistors (TFETs) based on homojunction direct-bandgap semiconductors. The model is based on an analytic description of two key features, which capture the main physical phenomena related to TFETs: (1) the potential profile from source to channel and (2) the elliptic curvature of the complex bands in the bandgap region. It is proposed to use 1D Poisson's equations in the source and the channel to describe the potential profile in homojunction TFETs. This allows to quantify the impact of source/drain doping on device performance, an aspect usually ignored in TFET modeling but highly relevant in ultra-scaled devices. The compact model is validated by comparison with state-of-the-art quantum transport simulations using a 3D full band atomistic approach based on non-equilibrium Green's functions. It is shown that the model reproduces with good accuracy the data obtained from the simulations in all regions of operation: the on/off states and the n branches of conduction. This approach allows calculation of energy-dependent band-to-band tunneling currents in TFETs, a feature that allows gaining deep insights into the underlying device physics. The simplicity and accuracy of the approach provide a powerful tool to explore in a quantitatively manner how a wide variety of parameters (material-, size-, and/or geometry-dependent) impact the TFET performance under any bias conditions. The proposed model presents thus a practical complement to computationally expensive simulations such as the 3D NEGF approach.
Strain-engineered self-organized InAs∕GaAs quantum dots for long wavelength (1.3 μm–1.5 μm) optical applications
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3295541
Configurable Electrostatically Doped High Performance Bilayer Graphene Tunnel FET
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2016
Innovative characterization techniques for ultra-scaled FinFETs
Publisher: IEEE
Date: 08-2010
Evolution of analog circuits on field programmable transistor arrays
Publisher: IEEE Comput. Soc
Date: 2000
Orbital Stark effect and quantum confinement transition of donors in silicon
Publisher: American Physical Society (APS)
Date: 09-10-2009
Theoretical study of strain-dependent optical absorption in a doped self-assembled InAs/InGaAs/GaAs/AlGaAs quantum dot
Publisher: Beilstein Institut
Date: 04-04-2018
DOI: 10.3762/BJNANO.9.99
Abstract: A detailed theoretical study of the optical absorption in doped self-assembled quantum dots is presented. A rigorous atomistic strain model as well as a sophisticated 20-band tight-binding model are used to ensure accurate prediction of the single particle states in these devices. We also show that for doped quantum dots, many-particle configuration interaction is also critical to accurately capture the optical transitions of the system. The sophisticated models presented in this work reproduce the experimental results for both undoped and doped quantum dot systems. The effects of alloy mole fraction of the strain controlling layer and quantum dot dimensions are discussed. Increasing the mole fraction of the strain controlling layer leads to a lower energy gap and a larger absorption wavelength. Surprisingly, the absorption wavelength is highly sensitive to the changes in the diameter, but almost insensitive to the changes in dot height. This behavior is explained by a detailed sensitivity analysis of different factors affecting the optical transition energy.
A tight-binding study of channel modulation in atomic-scale Si:P nanowires
Publisher: IEEE
Date: 09-2013
From Fowler–Nordheim to Nonequilibrium Green’s Function Modeling of Tunneling
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2016
Interface trap density metrology from sub-threshold transport in highly scaled undoped Si n-FinFETs
Publisher: AIP Publishing
Date: 15-12-2011
DOI: 10.1063/1.3660697
Abstract: Channel conductance measurements can be used as a tool to study thermally activated electron transport in the sub-threshold region of state-of-art FinFETs. Together with theoretical tight-binding (TB) calculations, this technique can be used to understand the dependence of the source-to-channel barrier height (Eb) and the active channel area (Saa) on three important parameters: (i) the gate bias (Vgs), (ii) the temperature, and (iii) the FinFET cross-section size. The quantitative difference between experimental and theoretical values that we observe can be attributed to the interface traps present in these FinFETs. Therefore, based on the difference between measured and calculated values of (i) Saa and (ii) |∂Eb/∂Vgs| (channel to gate coupling), two new methods of interface trap density (Dit) metrology are outlined. These two methods are shown to be very consistent and reliable, thereby opening new ways of analyzing in situ state-of-the-art multi-gate FETs down to the few nanometer width limit. Furthermore, theoretical investigation of the spatial current density reveals volume inversion in thinner FinFETs near the threshold voltage.
A single-atom transistor
Publisher: Springer Science and Business Media LLC
Date: 19-02-2012
Abstract: The ability to control matter at the atomic scale and build devices with atomic precision is central to nanotechnology. The scanning tunnelling microscope can manipulate in idual atoms and molecules on surfaces, but the manipulation of silicon to make atomic-scale logic circuits has been h ered by the covalent nature of its bonds. Resist-based strategies have allowed the formation of atomic-scale structures on silicon surfaces, but the fabrication of working devices-such as transistors with extremely short gate lengths, spin-based quantum computers and solitary dopant optoelectronic devices-requires the ability to position in idual atoms in a silicon crystal with atomic precision. Here, we use a combination of scanning tunnelling microscopy and hydrogen-resist lithography to demonstrate a single-atom transistor in which an in idual phosphorus dopant atom has been deterministically placed within an epitaxial silicon device architecture with a spatial accuracy of one lattice site. The transistor operates at liquid helium temperatures, and millikelvin electron transport measurements confirm the presence of discrete quantum levels in the energy spectrum of the phosphorus atom. We find a charging energy that is close to the bulk value, previously only observed by optical spectroscopy.
Gate-induced quantum-confinement transition of a single dopant atom in a silicon FinFET
Publisher: Springer Science and Business Media LLC
Date: 15-06-2008
DOI: 10.1038/NPHYS994
2D tunnel transistors for ultra-low power applications: Promises and challenges
Publisher: IEEE
Date: 10-2015
Can Homojunction Tunnel FETs Scale Below 10 nm?
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2016
Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting
Publisher: Springer Science and Business Media LLC
Date: 27-06-2013
DOI: 10.1038/NCOMMS3069
Abstract: Although silicon is a promising material for quantum computation, the degeneracy of the conduction band minima (valleys) must be lifted with a splitting sufficient to ensure the formation of well-defined and long-lived spin qubits. Here we demonstrate that valley separation can be accurately tuned via electrostatic gate control in a metal-oxide-semiconductor quantum dot, providing splittings spanning 0.3-0.8 meV. The splitting varies linearly with applied electric field, with a ratio in agreement with atomistic tight-binding predictions. We demonstrate single-shot spin read-out and measure the spin relaxation for different valley configurations and dot occupancies, finding one-electron lifetimes exceeding 2 s. Spin relaxation occurs via phonon emission due to spin-orbit coupling between the valley states, a process not previously anticipated for silicon quantum dots. An analytical theory describes the magnetic field dependence of the relaxation rate, including the presence of a dramatic rate enhancement (or hot-spot) when Zeeman and valley splittings coincide.
Stark tuning of the charge states of a two-donor molecule in silicon
Publisher: IOP Publishing
Date: 04-2011
DOI: 10.1088/0957-4484/22/22/225202
Abstract: A singly ionized two-donor molecule in silicon is an interesting test-bed system for implementing a quantum bit using charge degrees of freedom at the atomic limit of device fabrication. The operating principles of such a device are based on wavefunction symmetries defined by charge localizations and energy gaps in the spectrum. The Stark-shifted electronic structure of a two-donor phosphorus molecule is investigated using a multi-million-atom tight-binding framework. The effects of surface (S) and barrier (B) gates are analyzed for various voltage regimes. It is found that gate control is smooth for any donor separation, although at certain donor orientations the S and B gates may alter in functionality. Effects such as interface ionization, saturation of the lowest energy gap, and sensitivity to donor and gate placements are also investigated. Excited molecular states of P(2) + are found to impose limits on the allowed donor separations and operating gate voltages for coherent operation. This work therefore outlines and analyzes the various issues that are of importance in the design and control of such donor molecular systems.
Coherent electron transport by adiabatic passage in an imperfect donor chain
Publisher: American Physical Society (APS)
Date: 18-10-2010
Evolutionary design of electronic devices and circuits
Publisher: IEEE
Date: 1999
Combination of Equilibrium and Nonequilibrium Carrier Statistics Into an Atomistic Quantum Transport Model for Tunneling Heterojunctions
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2017
Statistical modeling of ultra-scaled donor-based silicon phosphorus devices
Publisher: IEEE
Date: 06-2014
Engineering the optical transitions of self-assembled quantum dots
Publisher: IEEE
Date: 09-2015
Spectroscopy of a deterministic single-donor device in silicon
Publisher: SPIE
Date: 05-2012
DOI: 10.1117/12.919763
Alloy Engineered Nitride Tunneling Field-Effect Transistor: A Solution for the Challenge of Heterojunction TFETs
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Atomistic Simulation of Non-Degeneracy and Optical Polarization Anisotropy in Pyramidal Quantum Dots
Publisher: IEEE
Date: 2007
Donor hyperfine Stark shift and the role of central-cell corrections in tight-binding theory
Publisher: IOP Publishing
Date: 18-03-2015
DOI: 10.1088/0953-8984/27/15/154207
Abstract: Atomistic tight-binding (TB) simulations are performed to calculate the Stark shift of the hyperfine coupling for a single arsenic (As) donor in silicon (Si). The role of the central-cell correction is studied by implementing both the static and the non-static dielectric screenings of the donor potential, and by including the effect of the lattice strain close to the donor site. The dielectric screening of the donor potential tunes the value of the quadratic Stark shift parameter (η2) from -1.3 × 10(-3) µm(2) V(-2) for the static dielectric screening to -1.72 × 10(-3) µm(2) V(-2) for the non-static dielectric screening. The effect of lattice strain, implemented by a 3.2% change in the As-Si nearest-neighbour bond length, further shifts the value of η2 to -1.87 × 10(-3) µm(2) V(-2), resulting in an excellent agreement of theory with the experimentally measured value of -1.9 ± 0.2 × 10(-3) µm(2) V(-2). Based on our direct comparison of the calculations with the experiment, we conclude that the previously ignored non-static dielectric screening of the donor potential and the lattice strain significantly influence the donor wave function charge density and thereby leads to a better agreement with the available experimental data sets.
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Publisher: IEEE
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