Low-dimensional Structures
|
Two-dimensional electron gas in Field-Effect Transistor
|
|
A modification to hetero-dimensional field effect transistors (HDFET)
has been studied and demonstrated to provide novel switching capabilities.
The modification consists of introducing a split drain into the
HDFET structure allowing the transistor to operate as a single pole -
double throw switch. By extension, multiple pole - multiple throw switches
can be made within a single transistor structure by introduction of
multiple split drains or sources. If the device is fabricated on
silicon germanium substrates, compatibility of the structure with
conventional CMOS processing is achievable, allowing for new applications
in digital, mixed signal, and high voltage switching.
Click here for simulated device operation
|
|
|
more
on the IP portfolio at Tyndall
|
Strained-Si Technology
|
|
Strained-Si appears as a potential technology for CMOS devices below 45 nm.
Strained-Si provides higher mobility and lower device access resistance
than crystalline Si. However an optimum trade-off between minimised
dopant diffusion and maximised dopant activation is necessary for the
formation of suitable shallow pn junctions.
Standard processing models are being adapted to predict doping diffusion
and activation in strained-Si, including the effect of Rapid Thermal Annealing.
Device modelling, incorporating experimental data from samples and
process modelling results, is then used to predict the behaviour of devices
fabricated on strained-Si. These simulations results help improve the
fabrication process (implantation and RTA) to achieve optimum device
characteristics.
|
|
|
|
Nicolas Cordero
|
Electronic and electrical characterisation of semiconductor nanowires
|
|
Quantum wires with a bulk Si core are investigated. It has been observed
that quantum confinement perpendicular to the wire axis gives rise to a
subband structure with a direct gap that can be tuned via the
cross-sectional diameter (picture on the left).
We look at effects of various surface terminations to the electronic
structure and their fingerprints on charge transport.
|
Click to view variation of bandgap with diameter
|
|
|
more on electronic transport
|
Sean O'Callaghan,
Giorgos Fagas,
Jim Greer
|
Quantum Effects
|
|
Driven by the exponential trend in the miniaturization of
microelectronics and advances in nanofabrication techniques,
circuit features, electronic devices and experimental prototypes
shrink at ever-smaller sizes approaching the nanoscale (~10nm).
At these lengths (or alternatively at low temperatures, ~K) quantum
phenomena dominate the elementary physical processes that determine
how the electric current flows. These regularly manifest in
measurements of charge-transport in artificially low-dimensional
semiconductor heterostructures or other structures of reduced physical
size such as etched semiconductor wires and self-assembled dots.
Much celebrated and/or widely applied in electronics are the
conductance quantization, its universal fluctuations and sub-quantization
features, single-electron transistor effects, and the variants of giant,
colossal and tunnelling magnetoresistance.
These arise from electrons being effectively confined in
small dimensions and to their correlated motion as a result of the
Coulomb interaction.
Our activities include the advancement of microscopic models contributing
to
- understanding the properties of fundamental excitations in
low-dimensional condensed matter systems,
- the development of accurate computational tools for
quantum mechanical electronic structure determination,
- and the design of transistor nanostructures that
underpin research in microelectronics and nanotechnology.
Both model and atomistically derived Hamiltonian descriptions are employed.
|
Proximity effects in wire and dot normal-superconducting hybrids
|
|
|
more on electronic transport
|
Giorgos Fagas
|
back to Electronics Theory page
|
