286 research outputs found
Monte Carlo Modeling of Spin FETs Controlled by Spin-Orbit Interaction
A method for Monte Carlo simulation of 2D spin-polarized electron transport
in III-V semiconductor heterojunction FETs is presented. In the simulation, the
dynamics of the electrons in coordinate and momentum space is treated
semiclassically. The density matrix description of the spin is incorporated in
the Monte Carlo method to account for the spin polarization dynamics. The
spin-orbit interaction in the spin FET leads to both coherent evolution and
dephasing of the electron spin polarization. Spin-independent scattering
mechanisms, including optical phonons, acoustic phonons and ionized impurities,
are implemented in the simulation. The electric field is determined
self-consistently from the charge distribution resulting from the electron
motion. Description of the Monte Carlo scheme is given and simulation results
are reported for temperatures in the range 77-300 K.Comment: 18 pages, 7 figure
Monte Carlo modeling of spin FETs controlled by spin-orbit interaction
A method for Monte Carlo simulation of 2D spin-polarized electron transport in III-V semiconductor heterojunction (FETs) is presented. In the simulation, the dynamics of the electrons in coordinate and momentum space is treated semiclassically. The density matrix description of the spin is incorporated in the Monte Carlo method to account for the spin polarization dynamics. The spin-orbit interaction in the spin FET leads to both coherent evolution and dephasing of the electron spin polarization. Spin-independent scattering mechanisms, including optical phonons, acoustic phonons and ionized impurities, are implemented in the simulation. The electric field is determined self-consistently from the charge distribution resulting from the electron motion. Description of the Monte Carlo scheme is given and simulation results are reported for temperatures in the range 77-300K. © 2004 IMACS. Published by Elsevier B.V. All rights reserved
Monte Carlo modeling of spin injection through a Schottky barrier and spin transport in a semiconductor quantum well
We develop a Monte Carlo model to study injection of spin-polarized electrons
through a Schottky barrier from a ferromagnetic metal contact into a
non-magnetic low-dimensional semiconductor structure. Both mechanisms of
thermionic emission and tunneling injection are included in the model. Due to
the barrier shape, the injected electrons are non-thermalized. Spin dynamics in
the semiconductor heterostructure is controlled by the Rashba and Dresselhaus
spin-orbit interactions and described by a single electron spin density matrix
formalism. In addition to the linear term, the third order term in momentum for
the Dresselhaus interaction is included. Effect of the Schottky potential on
the spin dynamics in a 2 dimensional semiconductor device channel is studied.
It is found that the injected current can maintain substantial spin
polarization to a length scale in the order of 1 micrometer at room temperature
without external magnetic fields.Comment: 18 pages, 4 figures, J. Appl. Phys., accepted for publicatio
Spin injection in spin FETs using a step-doping profile
We investigate effect of a step-doping profile on the spin injection from a
ferromagnetic metal contact into a semiconductor quantum well (QW) in spin FETs
using a Monte Carlo model. The considered scheme uses a heavily doped layer at
the metal/semiconductor interface to vary the Schottky barrier shape and
enhance the tunneling current. It is found that spin flux (spin current
density) is enhanced proportionally to the total current, and the variation of
current spin polarization does not exceed 20%.Comment: 5 pages, 8 figures. This paper is based on the work presented at the
2004 IEEE NTC Quantum Device Technology Workshop (Clarkson Unviersity,
Potsdam, NY, May 17-21, 2004), IEEE Transactions on Nanotechnology, accepted
for publicatio
Modeling for Semiconductor Spintronics
We summarize semiclassical modeling methods, including drift-diffusion,
kinetic transport equation and Monte Carlo simulation approaches, utilized in
studies of spin dynamics and transport in semiconductor structures. As a review
of the work by our group, several examples of applications of these modeling
techniques are presented.Comment: 31 pages, 9 figure
Spin recovery in the 25nm gate length InGaAs field effect transistore
We augmented an ensemble Monte-Carlo semiconductor device simulator [3] to incorporate electron spin degrees of freedom using a Bloch equation model to investigate the feasibility of spintronic devices. Results are presented for the steady state polarization and polarization decay due to scattering and spin orbit coupling for a III-V MOSFET device as a function of gate voltages, injection polarization and strain
Spin recovery in the 25nm gate length InGaAs field effect transistore
We augmented an ensemble Monte-Carlo semiconductor device simulator [3] to incorporate electron spin degrees of freedom using a Bloch equation model to investigate the feasibility of spintronic devices. Results are presented for the steady state polarization and polarization decay due to scattering and spin orbit coupling for a III-V MOSFET device as a function of gate voltages, injection polarization and strain
Double-Free-Layer Stochastic Magnetic Tunnel Junctions with Synthetic Antiferromagnets
Stochastic magnetic tunnel junctions (sMTJ) using low-barrier nanomagnets
have shown promise as fast, energy-efficient, and scalable building blocks for
probabilistic computing. Despite recent experimental and theoretical progress,
sMTJs exhibiting the ideal characteristics necessary for probabilistic bits
(p-bit) are still lacking. Ideally, the sMTJs should have (a) voltage bias
independence preventing read disturbance (b) uniform randomness in the
magnetization angle between the free layers, and (c) fast fluctuations without
requiring external magnetic fields while being robust to magnetic field
perturbations. Here, we propose a new design satisfying all of these
requirements, using double-free-layer sMTJs with synthetic antiferromagnets
(SAF). We evaluate the proposed sMTJ design with experimentally benchmarked
spin-circuit models accounting for transport physics, coupled with the
stochastic Landau-Lifshitz-Gilbert equation for magnetization dynamics. We find
that the use of low-barrier SAF layers reduces dipolar coupling, achieving
uncorrelated fluctuations at zero-magnetic field surviving up to diameters
exceeding ( nm) if the nanomagnets can be made thin enough
(- nm). The double-free-layer structure retains bias-independence
and the circular nature of the nanomagnets provides near-uniform randomness
with fast fluctuations. Combining our full sMTJ model with advanced transistor
models, we estimate the energy to generate a random bit as 3.6 fJ,
with fluctuation rates of 3.3 GHz per p-bit. Our results will guide
the experimental development of superior stochastic magnetic tunnel junctions
for large-scale and energy-efficient probabilistic computation for problems
relevant to machine learning and artificial intelligence
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