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Dr R A Oliver and Dr L C Hirst

The first half of the lecture course will introduce a range of optoelectronic devices including light emitting diodes,and laser diodes.  It will initially address the underlying physics of the quantum structures used in such systems, using the Schrodinger equation to understand the energy levels and the density of states in quantum wells, wires and dots.  This will then enable discussion of the advantages of using quantum structures in light emitting devices.

Thereafter, the crystal growth technologies used to fabricate quantum structures will be introduced, with an emphasis on molecular beam epitaxy and metal organic vapour phase epitaxy.  By understanding the mechanisms by which epitaxial semiconductor growth proceeds, we will reveal methods for the self-assembly and self-organisation of quantum structures.

Finally, in the first half of the course, a research case study on single photon sources will illustrate how the physical principles and practical techniques which have been discussed are being used in current research on single photon emitters to develop light sources for use in secure data communication.  The aim is to expose the students to state-of-the-art research and to illustrate the potential real world impact of the nanotechnologies which have been introduced.

The second half of the lecture course will take a broad look at the semiconductor materials family comparing group IV materials with III-V alloys to qualitatively understand how bonding affects the observed electronic and optical properties of these materials. Complex III-V alloys provide a palette of materials for device design with a range of properties. The semi-empirical rules which govern the properties of III-V alloys including lattice constant, bandgap and band-alignment will be discussed.

A gradient in chemical potential is a key requirement to drive charge carrier motion and enable useful electrical functionality. The layering of materials, with different properties to form devices is discussed, in particular pn junctions and ideal and non-ideal diode behaviour. Different diode regimes of operation are described: forward bias (LED/laser), reverse bias (detector), power generation (solar cell).

Photovoltaic devices are explored in more detail as a model optoelectronic system. Limiting efficiencies are derived using a detailed balance formalism and new emerging technologies for achieving high efficiency are discussed along with critical materials requirements for terrestrial and space systems.