159 research outputs found
A Dual Gate Spin Field Effect Transistor With Very Low Switching Voltage and Large ON-to-OFF Conductance Ratio
We propose and analyze a novel dual-gate Spin Field Effect Transistor
(SpinFET) with half-metallic ferromagnetic source and drain contacts. The
transistor has two gate pads that can be biased independently. It can be
switched ON or OFF with a few mV change in the differential bias between the
two pads, resulting in extremely low dynamic power dissipation during
switching. The ratio of ON to OFF conductance remains fairly large (~ 60) up to
a temperature of 10 K. This device also has excellent inverter characteristics,
making it attractive for applications in low power and high density Boolean
logic circuits
The Effect of Ramsauer Type Transmission Resonances on the Conductance Modulation of Spin Interferometers
We use a mean field approach to study the conductance modulation of gate
controlled semiconductor spin interferometers based on the Rashba spin-orbit
coupling effect. The conductance modulation is found to be mostly due to
Ramsauer type transmission resonances rather than the Rashba effect in typical
structures. This is because of significant reflections at the interferometer's
contacts due to large potential barriers and effective mass mismatch between
the contact material and the semiconductor. Thus, unless particular care is
taken to eliminate these reflections, any observed conductance modulation of
spin interferometers may have its origin in the Ramsauer resonances (which is
unrelated to spin) rather than the Rashba effect.Comment: 3 figure
A spin field effect transistor for low leakage current
In a spin field effect transistor, a magnetic field is inevitably present in
the channel because of the ferromagnetic source and drain contacts. This field
causes random unwanted spin precession when carriers interact with non-magnetic
impurities. The randomized spins lead to a large leakage current when the
transistor is in the ``off''-state, resulting in significant standby power
dissipation. We can counter this effect of the magnetic field by engineering
the Dresselhaus spin-orbit interaction in the channel with a backgate. For
realistic device parameters, a nearly perfect cancellation is possible, which
should result in a low leakage current.Comment: To appear in Physica E. The revised version has additional material
which addresses the issue of which way the contacts should be magnetized in a
Spin Field Effect Transistor. This was neither addressed in the previous
version, nor in the upcoming journal pape
A Digital Switch and Femto-Tesla Magnetic Field Sensor Based on Fano Resonance in a Spin Field Effect Transistor
We show that a Spin Field Effect Transistor, realized with a semiconductor
quantum wire channel sandwiched between half-metallic ferromagnetic contacts,
can have Fano resonances in the transmission spectrum. These resonances appear
because the ferromagnets are half-metallic, so that the Fermi level can be
placed above the majority but below the minority spin band. In that case, the
majority spins will be propagating, but the minority spins will be evanescent.
At low temperatures, the Fano resonances can be exploited to implement a
digital binary switch that can be turned on or off with a very small gate
voltage swing of few tens of microvolts, leading to extremely small dynamic
power dissipation during switching. An array of 500,000 x 500,000 such
transistors can detect ultrasmall changes in a magnetic field with a
sensitivity of 1 femto-Tesla/sqrt{Hz}, if each transistor is biased near a Fano
resonance
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