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A two-dimensional, steady state Monte Carlo (MC) device simulator which is especially suited €or the simulation of submicron MOSFETs is described. A unique Monte Carlo-Poisson coupling scheme has been adopted, which exhibits a... more
A two-dimensional, steady state Monte Carlo (MC) device simulator which is especially suited €or the simulation of submicron MOSFETs is described. A unique Monte Carlo-Poisson coupling scheme has been adopted, which exhibits a significantly better convergence rate than conventional schemes. This technique is based on MC-DriftDiffusion (DD) coupling, a method which proves to be correct within the Boltsmann formalism. In
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An approach for analysis of the small signal response of the carriers in semiconductors is presented. The response to an impulse signal is explained in terms of a relaxation process, governed by a Boltzmann equation. The approach assists... more
An approach for analysis of the small signal response of the carriers in semiconductors is presented. The response to an impulse signal is explained in terms of a relaxation process, governed by a Boltzmann equation. The approach assists the understanding of the phenomenon and allows development of novel stochastic algorithms
Research Interests: Computer Science, Physics, Microelectronics, Signal Processing, Monte Carlo Simulation, and 15 moreKinetics, Semiconductors, Statistical Physics, Integral Equations, Monte Carlo Methods, Signal Analysis, Kinetic Theory, Computation, Semiconductor, Impulse response, Frequency, Steady state, Boltzmann equation, Stochastic Algorithm, and Monte Carlo Method
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A transport model for quantum cascade lasers based on the Pauli master equation is presented. An efficient Monte Carlo solver has been developed. The numerical methods to reduce the computational cost are discussed in detail. Finally, the... more
A transport model for quantum cascade lasers based on the Pauli master equation is presented. An efficient Monte Carlo solver has been developed. The numerical methods to reduce the computational cost are discussed in detail. Finally, the simulator is used to obtain current-voltage characteristics as well as microscopic quantities of a mid-infrared QCL structure.
The theoretical foundations of the backward Monte Carlo (BMC) method for the solution of the semiconductor Boltzmann equation have been laid out three decades ago [1][2]. A modified version of the BMC algorithm that guarantees numerical... more
The theoretical foundations of the backward Monte Carlo (BMC) method for the solution of the semiconductor Boltzmann equation have been laid out three decades ago [1][2]. A modified version of the BMC algorithm that guarantees numerical stability has been developed recently and implemented in a full-band MC device simulator [3]. We have studied the electrical characteristics of a 65nm n-channel MOSFET. The BMC method allows one to calculate the drain current in the entire sub-threshold region including the leakage current in the off-state. Compuation times are on the order of 10 seconds for frozenfield simulations (Fig 1). The current through a plane is calculated by means of MC integration of the current density. For this integration a distribution of the sampling points has to be assumed which, in the present case, represent the initial states of the backward trajectories. In this work we discuss the properties of the current estimators obtained from different choices of that dist...
In contrast to narrow bandgap semiconductors such as silicon, common doping elements in SiC have activation energies larger than the thermal energy kB Teven at room temperature. Inequivalent α-SiC sites, one with cubic (k) surrounding and... more
In contrast to narrow bandgap semiconductors such as silicon, common doping elements in SiC have activation energies larger than the thermal energy kB Teven at room temperature. Inequivalent α-SiC sites, one with cubic (k) surrounding and the other with hexagonal (h) surrounding are expected to cause site-dependent impurity levels. Therefore, an appropriate incomplete ionization model which accounts for lattice sitedependent ionization level of impurities in a-SiC has been developed and implemented in the general-purpose device simulator MINIMOS-NT.
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Beads made from Egyptian faience have been excavated from grave deposits (c. 4000–3100 BC), together with beads of glazed steatite (a soft rock) and of semiprecious stones such as turquoise, carnelian, quartz, and lapis lazuli.... more
Beads made from Egyptian faience have been excavated from grave deposits (c. 4000–3100 BC), together with beads of glazed steatite (a soft rock) and of semiprecious stones such as turquoise, carnelian, quartz, and lapis lazuli. Information on these and many more ancient beads used for ornaments and jewelry, ritual ceremonies, as art artifacts and gifts for amorous women throughout history, and descriptions of the raw materials (e.g., glass, bone, precious and other stones) and manufacturing technologies used for their production can be located in many references. Many books are devoted to the description of beads that are not of water-soluble polymer origin, techniques for their production, their art, value, and distribution, reflecting the wealth of information existing in this field of science and art. On the other hand, there are no books fully devoted to the fascinating topic of hydrocolloid (polymeric) beads and their unique applications. A few books contain scattered chapters ...
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1. Abstract Low-field mobilities for (100) and (110) substrate orientations in single-gate (SG) and double-gate (DG) operation modes are compared. It is argued that for the same gate voltage twice as high carrier concentration in DG... more
1. Abstract Low-field mobilities for (100) and (110) substrate orientations in single-gate (SG) and double-gate (DG) operation modes are compared. It is argued that for the same gate voltage twice as high carrier concentration in DG ultra-thin body (UTB) SOI as compared to the SG mode leads to a higher relative occupation of primed subband ladder for (100) substrate orientation. Efficient scattering in primed subbands overpowers the mobility enhancement due to the volume inversion in DG and leads to a lower DG mobility at high effective fields as compared to that for SG UTB SOI.
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1. Abstract Uniaxial [110] stress induced valley shifts and effective masses modifications are analyzed. Analytical expressions for both transversal and longitudinal masses are obtained for the first time. Analytical results are verified... more
1. Abstract Uniaxial [110] stress induced valley shifts and effective masses modifications are analyzed. Analytical expressions for both transversal and longitudinal masses are obtained for the first time. Analytical results are verified with pseudo-potential band structure calculations and excellent agreement is found. The low-field mobility enhancement in the direction of tensile [110] stress is due to the conductivity mass modification and is shown to exist in SOIs with arbitrary small body thickness.
A MoS 2 sheet in its 1 T ' phase is a two-dimensional topological insulator. It possesses highly conductive edge states which, due to topological protection, are insensitive to back scattering and are suitable for device channels. A... more
A MoS 2 sheet in its 1 T ' phase is a two-dimensional topological insulator. It possesses highly conductive edge states which, due to topological protection, are insensitive to back scattering and are suitable for device channels. A transition between the topological and conventional insulator phases in a wide 1 T '-MoS 2 sheet is controlled by an electric field orthogonal to the sheet. In order to enhance the current through the channel several narrow nanoribbons are stacked. We evaluate the subbands in a narrow nanoribbon of 1 T '-MoS 2 by using an effective k ∙ p Hamiltonian. In contrast to a wide channel, a small gap in the spectrum of edge states in a nanoribbon increases with the electric field. It results in a rapid decrease in the nanoribbon conductance with the field, making it potentially suitable for current switching.
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We discuss boundary value problems for the characteristic stationary von Neumann equation (stationary sigma equation) and the stationary Wigner equation in a single spatial dimension. The two equations are related by a Fourier transform... more
We discuss boundary value problems for the characteristic stationary von Neumann equation (stationary sigma equation) and the stationary Wigner equation in a single spatial dimension. The two equations are related by a Fourier transform in the non-spatial coordinate. In general, a solution to the characteristic equation does not produce a corresponding Wigner solution as the Fourier transform will not exist. Solution of the stationary Wigner equation on a shifted k-grid gives unphysical results. Results showing a negative differential resistance in IV-curves of resonant tunneling diodes using Frensley’s method are a numerical artefact from using upwinding on a coarse grid. We introduce the integro-differential sigma equation which avoids distributional parts at $$k=0$$ k = 0 in the Wigner transform. The Wigner equation for $$k=0$$ k = 0 represents an algebraic constraint needed to avoid poles in the solution at $$k=0$$ k = 0 . We impose the inverse Fourier transform of the integrabi...
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ABSTRACT
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N-type SnSe compound has been synthesized through melting with spark plasma sintering. By doping BiCl3, the carrier concentration of SnSe is significantly increased, leading to a large enhancement of electrical conductivity. Meanwhile,... more
N-type SnSe compound has been synthesized through melting with spark plasma sintering. By doping BiCl3, the carrier concentration of SnSe is significantly increased, leading to a large enhancement of electrical conductivity. Meanwhile, the SnSe0.95-BiCl3 samples also exhibit higher Seebeck coefficient and lower lattice thermal conductivity, compared with polycrystalline SnSe. Consequently, a high power factor of ∼5 μW cm−1 K−2 and a ZT of 0.7 have been achieved at 793 K. The synergistic roles of BiCl3 doping in SnSe provide many opportunities in the optimization of n-type SnSe materials.
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Research Interests: Physics, Condensed Matter Physics, Very Low Frequency Electromagnetics, Low Frequency, Numerical Simulation, and 12 moreShot Noise, Scaling, Coulomb, Spectrum, Coulomb blockade, Low Temperature, Fano factor, Spectral Density, Electric Field, Unsolved Problems, Thermal fluctuation, and Current fluctuation
Due to the ongoing downscaling of devices non-local effects become more and more important. These non-local effects can be considered in a device simulator using a hydrodynamic (HD) transport model. However, solving the equation system... more
Due to the ongoing downscaling of devices non-local effects become more and more important. These non-local effects can be considered in a device simulator using a hydrodynamic (HD) transport model. However, solving the equation system resulting from a HD transport model is known to be much more expensive in computational terms compared to the simpler drift-diffusion (DD) transport model. Thus the HD model should only be used when really necessary in order not to waste valuable computational resources. However, the validity of the DD model must be carefully investigated which is subject to this paper.
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The influence of dopant species on electron mobility in GaAs is investigated. Based on Thomas-Fermi theory to describe the charge density of the individual impurity ion we derive an analytical expression for the scattering rate. Employing... more
The influence of dopant species on electron mobility in GaAs is investigated. Based on Thomas-Fermi theory to describe the charge density of the individual impurity ion we derive an analytical expression for the scattering rate. Employing these results in a Monte Carlo calculation we fi nd a signifi cant dependence of mobility on donor species for concentrations beyond cm .
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ABSTRACT