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Novel nanocavities in wide bandgap semiconductors for quantum optical devices

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  • Full or part time
    Dr Daryl Beggs
    Dr A Bennett
  • Application Deadline
    No more applications being accepted
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

Nanoscale cavities change the optical density of states for localised emitters in semiconductors, changing their optical properties. A famous example is the Purcell effect where a single optical mode is localised in a small volume of space with a narrow frequency width, leading photon emission being preferentially guided into a single mode with high efficiency and high rate. To realise these cavities the semiconductor must be structured on a length scale smaller than one wavelength.

The project will develop a novel processing technique to create gallium nitride (GaN) optical nanocavities. GaN is a commercially important semiconductor [1] with widespread use in solid state lighting, blue lasers and high power transistors. We will optimise the processing of GaN on various crystal planes by using an angled Faraday cage over the sample to create an angled inductively coupled plasma (ICP) etch [2]. We will demonstrate new geometries of optical cavity which use fewer fabrication steps, simplifying the processing of manufacturable devices.

The objective of the project is to design, create and test optical cavities in GaN by angled etching. The angled etching is already developed in the ACES feasibility study, so the project can begin delivering useful devices. You will create photonic crystal beams (which can lead to lasers with ultra-low threshold) and micro-discs (which can be used for lasers, frequency conversion and gas sensing) [3]. The project will also involve optical characterisation within a newly equipped lab with single photon sensitive detectors, high speed electronics and single frequency lasers.

The project will be completed within 3.5 years by following the structure:
Year 1 – understand the project
The student will perform a literature review and prepare a PhD project plan. They will start learning the software for numerical simulations (Lumerical FDTD and Mode), as well as undergo cleanroom training. They will start training on optical characterisation in the laboratory.
Year 2 – substantial research
The student will develop and optimise the fabrication procedures needed to make the devices. They will characterise and test these devices in the laboratory, and compare the results against their own design specifications and theoretical models.
Year 3 – becoming an independent researcher
The student will now be an expert in all aspects of the project, able to make independent contributions and will begin to write-up the results for dissemination.
Final 6 months – finishing research and starting writing up.
Throughout, the student will be monitored via the usual PHYSX procedures. This includes an initial review after 3 months, and an Annual Review after 9, 21, and 33 months (all recorded on SIMS), with interim reviews conducted midway.

Funding Notes

Full UK/EU tuition fees plus stipend matching UKRI Minimum.

Full awards are open to UK Nationals and EU students who meet UK residency requirements. To be eligible for the full award, EU Nationals must have been in the UK for at least three years prior to the start of the course including for full-time education.

A small number of awards may also be made available to EU Nationals who do not meet the above residency requirement, provided they have been ordinarily resident in the EU for at least three years before the start of their proposed programme of study.


[2] Nature Communications. 5, 5718 (2014)
[3] T. Zhu et al, Nitride Quantum Light Sources, Euro. Phys. Lett. 113, 38001 (2016).

Related Subjects

How good is research at Cardiff University in Physics?

FTE Category A staff submitted: 19.50

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