Controlling electron-phonon interactions through phonon cavity engineering

PhD opportunity at the University of New South Wales, Sydney, Australia

The School of Photovoltaic and Renewable Energy Engineering (SPREE) is widely regarded as the one of the leading Photovoltaics research hubs in the world. Building on its world-leading research, the school attracts leading international researchers in the area of photovoltaic, consistently ranked amongst the leaders worldwide in the photovoltaic field through international peer review. It is one of the nine schools within the Faculty of Engineering at University of New South Wales (UNSW), Sydney, Australia and grew out of the Australian Research Council Photovoltaics Centre of Excellence in response to the growing photovoltaic and renewable energy industry.

We are looking for an excellent student for a novel project looking at phonon cavity design and characterisation. This will build on recent results obtained by the group of A/Prof Stephen Bremner that has demonstrated high quality AlAs/GaAs phonon cavities with the ability to modify the electron-phonon interaction in these structures. The main techniques to be used will be time resolved photoluminescence and transient reflectivity. There is also the possibility of engaging in the growth of samples using the Gen930 molecular beam epitaxy system that is part of the Australian Nanofabrication Facility (ANFF https://www.anff-nsw.org/). Detailed characterisation of the samples by methods such as X-ray Diffraction is also envisaged.

SPREEs Research Activities

UNSW has been responsible for developing the most successfully commercialised new photovoltaic technology internationally. Most of the solar cell technology that dominates the market (in particular the ‘PERC’ design) was invented and developed here. Currently there are a wide range of activities in the school spanning novel processing techniques for improved performance of commercial silicon cells, advanced characterisation techniques, integrating silicon with novel materials for the development of multi-junction solar cells, as well as advanced concepts for totally new approaches to photovoltaic device designs. There is a growing capability for fabrication and characterisation of III-V based material device structures.

Investigation of phonon cavities for the study of electron-phonon interactions

The aim of this project is to design and study in detail of phonon cavity structures for the study and manipulation of carrier-phonon interactions. The design approach initially will be adiabatic potential cavity structures, realised in III-V compound semiconductors, building on results already obtained. Studies of the properties of the III-V based phonon cavity samples will be conducted using transient reflectivity measurements and time resolved photoluminescence for the electron dynamics. As part of the project designs for samples incorporating phonon cavities to allow for probing of the impact of the modified phonon spectrum on electron-phonon interactions will be synthesized and tested. The ultimate aim is to use phonon cavities to induce so-called ‘phonon bottlenecks’ where the relaxation of energetic electrons to the hosts band edges is frustrated leading to hot carrier effects.

The main project aims are to:

·        Study in detail the properties of phonon cavity samples designed using adiabatic phonon potentials by techniques like transient reflectivity.

·        Detailed study of the electron-phonon interactions in designed samples using techniques such as time resolved photoluminescence.

·        Experimental investigation of the manipulation of the phonon spectrum in samples to modify electron-phonon interactions, with a view to inducing phonon bottlenecks for hot carrier effects.

Requirements

Undergraduate Degree: Bachelor degree in Electrical Engineering, Physics or Materials Science or similar. Overall GPA must be at least 80%.

Masters Degree: Priority will be given for those who graduated from a Masters by research program, with a strong semiconductor physics emphasis, can be theoretical or experimental focussed. Overall GPA must be at least 80%.

Prior research experience is considered key for competitive scholarships for international students.

The supervision team would consist of A/Prof Stephen Bremner and Dr Michael Nielsen

For more details please contact A/Prof Stephen Bremner (spbremner@unsw.edu.au).