Researchers within the QED group are investigating
the electrical and optical properties of nanometer scale semiconductor
devices. At these small length scales the device properties are no longer
governed by semi-classical physics, but are instead determined by quantum
mechanical effects. The group makes its own quantum semiconductor devices
here at UNSW, and uses a variety of electronic probes, at milliKelvin
temperatures and in strong magnetic fields, to further the understanding
of quantum electronics.
Quantum and transport scattering in 2D systems
2D electron systems formed in Si and GaAs field effect transistors underpin
the modern computing and communications industries, in addition to being
the starting point for investigations of new physical phenomena in quantum
devices.
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| Schematic cross-section
of a generic AlGaAs/GaAs heterostructure. Ni3D
is the density of RII dopants, NB1 and NB2
are the densities of the BG impurities in the AlGaAs and
GaAs respectively, a
is the width of the AlGaAs spacer layer and t,
the width of the doped AlGaAs region. |
Band diagram for a AlGaAs/GaAs
heterostructure. The 2DEG forms at the triangular well
at the AlGaAs-GaAs heterointerface |
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Transport in a two-dimensional electron gas (2DEG) is strongly
affected by disorder.
We examine the low-temperature properties of high-quality heterostructures,
in which scattering is dominated by two types of
disorder: remote ionised impurities (RII) and homogeneous background
(BG) impurities.
The two charactersitic scattering times are the transport lifetime
tt, and the quantum scattering time tq:
However it turns out calculations involving the homogeneous background
impurities, which effects quantum device performance is non-trivial
and hinders direct comparison between theory and experiment.
We are developing new techniques to simplify calculations of Coulomb
scattering in two-dimensional systems. This will facilitate comparisons
between theory and experiment, and allow expermentalists to determine
what kind of disorder is dominant in their devices.
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