Current research:
Quantum and transport scattering lifetimes
in two dimensional systems


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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.
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












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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Updated: 3-Oct-2002