We have two main activities investigating the physics and device applications of semiconductor nanowires:

Deterministic single photon sources

In emerging quantum information applications it is very likely that deterministic site-control of quantum dots (QDs) will form a vital requirement for multi-quantum bit (qubit) scale-up. The considerable difficulties in controlling QD location and emission properties in the most common self-assembled systems has motivated research into alternative methods of QD formation. Our approach consists of growing QDs in nanowires (NWQDs) in which few-nanometers thick layers of lower bandgap material are grown within the wider bandgap material of the nanowire. The lateral size, height and density of QDs are then controlled by the nanowire diameter, growth time, and nanowire density. Optical spectroscopic studies of NWQDs reveal narrow emission linewidths and photon antibunching, important properties of single photon sources for quantum information applications.

An SEM image of a typical nanowire array, with dimensions of nanowires indicated.

An SEM image of a typical nanowire array, with dimensions of nanowires indicated.

Nanowire solar cells

III-V nanowire array solar cells provide intrinsic light trapping due to multiple scattering events and preferential coupling of photons into optical modes supported by the array. This may allow for a significant reduction in material consumption relative to planar solar cells, whilst still achieving strong light absorption within the nanowire array. Combining nanowire arrays with conventional, planar silicon solar cells offers a promising route to enhancing present-day solar cell efficiencies. Our simulations show that with realistic design parameters for a III-V nanowire- silicon bottom cell system an efficiency enhancement of 25% relative to a planar silicon cell can be achieved. We are presently investigating nanowire solar cells based on these designs in our labs.

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