The prospects for 10 nm III-V CMOS

The increasing difficulties for further scaling down of Si CMOS is bringing to the fore the investigation of alternative channel materials. Among these, III-V compound semiconductors are very attractive due to their outstanding electron transport properties. This paper briefly reviews the prospects and the challenges for a III-V CMOS technology with gate lengths in the 10 nm range.Semiconductor Research CorporationIntel Corporatio

Probing Spin-Charge Separation in Tunnel-Coupled Parallel Quantum Wires

Interactions in one-dimensional (1D) electron systems are expected to cause a dynamical separation of electronic spin and charge degrees of freedom. A promising system for experimental observation of this non-Fermi-liquid effect consists of two quantum wires coupled via tunneling through an extended uniform barrier. Here we consider the minimal model of an interacting 1D electron system exhibiting spin-charge separation and calculate the differential tunneling conductance as well as the density-density response function. Both quantities exhibit distinct strong features arising from spin-charge separation. Our analysis of these features within the minimal model neglects interactions between electrons of opposite chirality and applies therefore directly to chiral 1D electron systems realized, e.g., at the edge of integer quantum-Hall systems. Physical insight gained from our results is useful for interpreting current experiment in quantum wires as our main conclusions still apply with nonchiral interactions present. In particular, we discuss the effect of charging due to applied voltages, and the possibility to observe spin-charge separation in a time-resolved experiment.Comment: 9 pages, 3 figures, expanded version with many detail

Conductance oscillations in strongly correlated fractional quantum Hall line junctions

We present a detailed theory of transport through line junctions formed by counterpropagating single-branch fractional-quantum-Hall edge channels having different filling factors. Intriguing transport properties are exhibited when strong Coulomb interactions between electrons from the two edges are present. Such strongly correlated line junctions can be classified according to the value of an effective line-junction filling factor n that is the inverse of an even integer. Interactions turn out to affect transport most importantly for n=1/2 and n=1/4. A particularly interesting case is n=1/4 corresponding to, e.g., a junction of edge channels having filling factor 1 and 1/5, respectively. We predict its differential tunneling conductance to oscillate as a function of voltage. This behavior directly reflects the existence of novel Majorana-fermion quasiparticle excitations in this type of line junction. Experimental accessibility of such systems in current cleaved-edge overgrown samples enables direct testing of our theoretical predictions.Comment: 2 figures, 10 pages, RevTex4, v2: added second figure for clarit

Parameter identification problems in the modelling of cell motility

We present a novel parameter identification algorithm for the estimation of parameters in models of cell motility using imaging data of migrating cells. Two alternative formulations of the objective functional that measures the difference between the computed and observed data are proposed and the parameter identification problem is formulated as a minimisation problem of nonlinear least squares type. A Levenberg–Marquardt based optimisation method is applied to the solution of the minimisation problem and the details of the implementation are discussed. A number of numerical experiments are presented which illustrate the robustness of the algorithm to parameter identification in the presence of large deformations and noisy data and parameter identification in three dimensional models of cell motility. An application to experimental data is also presented in which we seek to identify parameters in a model for the monopolar growth of fission yeast cells using experimental imaging data. Our numerical tests allow us to compare the method with the two different formulations of the objective functional and we conclude that the results with both objective functionals seem to agree

Mesoscopic effects in tunneling between parallel quantum wires

We consider a phase-coherent system of two parallel quantum wires that are coupled via a tunneling barrier of finite length. The usual perturbative treatment of tunneling fails in this case, even in the diffusive limit, once the length L of the coupling region exceeds a characteristic length scale L_t set by tunneling. Exact solution of the scattering problem posed by the extended tunneling barrier allows us to compute tunneling conductances as a function of applied voltage and magnetic field. We take into account charging effects in the quantum wires due to applied voltages and find that these are important for 1D-to-1D tunneling transport.Comment: 8 pages, 7 figures, improved Figs., added Refs. and appendix, to appear in Phys. Rev.

Testing Bell's inequality using ballistic electrons in semiconductors

We propose an experiment to test Bell's inequality violation in condensed-matter physics. We show how to generate, manipulate, and detect entangled states using ballistic electrons in Coulomb-coupled semiconductor quantum wires. Due to its simplicity (only five gates are required to prepare entangled states and to test Bell's inequality), the proposed semiconductor-based scheme can be implemented with currently available technology. Moreover, its basic ingredients may play a role towards large-scale quantum-information processing in solid-state devices

Heteroepitaxy of La2O3La_2O_3 and La2−xYxO3La_{2-x}Y_xO_3 on GaAs (111)A by Atomic Layer Deposition: Achieving Low Interface Trap Density

GaAs metal–oxide–semiconductor devices historically suffer from Fermi-level pinning, which is mainly due to the high trap density of states at the oxide/GaAs interface. In this work, we present a new way of passivating the interface trap states by growing an epitaxial layer of high-k dielectric oxide, $La_{2–x}Y_xO_3$, on GaAs(111)A. High-quality epitaxial $La_{2–x}Y_xO_3$ thin films are achieved by an ex situ atomic layer deposition (ALD) process, and GaAs MOS capacitors made from this epitaxial structure show very good interface quality with small frequency dispersion and low interface trap densities $(D_{it})$. In particular, the $La_2O_3$/GaAs interface, which has a lattice mismatch of only 0.04%, shows very low $D_{it}$ in the GaAs bandgap, below $3 × 10^{11} cm^{–2} eV^{–1}$ near the conduction band edge. The $La_2O_3$/GaAs capacitors also show the lowest frequency dispersion of any dielectric on GaAs. This is the first achievement of such low trap densities for oxides on GaAs.Chemistry and Chemical Biolog

High-Frequency (> 100 GHz) and High-Speed (< 10 ps) Electronic Devices

Contains an introduction, reports on four research projects and a list of publications.Defense Advanced Research Projects Agency Contract MDA972-90-C-0021National Aeronautics and Space Administration Grant NAGW-4691National Aeronautics and Space Administration Grant 959705National Science Foundation Grant AST 94-23608National Science Foundation/MRSEC Grant DMR 94-00334MIT Lincoln Laboratory Advanced Concept Program Grant BX-5464U.S. Army Research Office Grant DAAH04-95-1-0610Hertz Foundation FellowshipU.S. Army - Office of Scientific Research Grant DAAH04-94-G-016

High-Frequency (>100 GHz) and High-Speed (<1 ps) Electronic Devices

Contains an introduction, reports on three research projects and a list of publications.Advanced Research Projects Agency Contract MDA972-90-C-0021National Aeronautics and Space Administration Grant NAG2-693National Aeronautics and Space Administration Contract 959705National Science Foundation/MRSEC Grant DMR 94-00334MIT Lincoln Laboratory Advanced Concept Program Contract BX-5464MIT Research Laboratory of Electronics Postdoctoral FellowshipRome Air Force Laboratory Graduate FellowshipU.S. Army Research Office Grant DAAL03-92-G-0251Hertz Foundation FellowshipU.S. Army Research Office/ASSERT Grant DAAH04-94-G-016