Development of III-N Site-Controlled Quantum Dots
: (Alternative Format Thesis)

Student thesis: Doctoral ThesisPhD


Quantum information science (QIS) has the potential to revolutionise technology and, indeed, modern day life as as we know it. Applications range from vastly improved encryption technology in the form of quantum key distribution to revolutionising computation in the form of quantum computing. Development of the latter could drastically change the ability to model many systems from financial markets to the folding of proteins. There are a number of different technologies being developed to realise quantum information applications ranging from photonics to superconducting architectures. Semiconductor quantum dots are particularly attractive solutions for QIS applications due to the possibility of their integration with existing, mature, semiconductor technology. In particular, site-controlled quantum dots (SCQDs) could revolutionise QIS by wafer scale fabrication and growth of large numbers of quantum devices. This is as SCQD technology has the ease of scalability whereby it can be developed on smaller samples and then extended to be manufactured on the wafer scale.

The III-N's materials group hold a great deal of promise for site-controlled quantum dot applications owing to their large band-gap off-sets and large excitonic binding energies allowing for the creation of quantum devices that could operate at or close to room temperature. The GaN/AlN system is particularly promising for such endeavours, however, due to the difficulty in creating uniform arrays of AlN sites to house GaN quantum dots, this area of the field has been largely unexplored.

In this thesis, regular arrays of spatially predetermined, faceted AlN nanostructures, suitable to house GaN quantum dots are realised. This is achieved by combining top-down dry etching with bottom-up regrowth. The dynamics of the regrowth step are explored and explained. This is followed by the exploration of a combination of dry and wet etching, in order to again realise periodic arrays of AlN nanostructures. The aspect ratios of the dry etched nanostructures after wet etching were investigated and a model of the wet etching dynamics was proposed. Additionally, thermal etching and an investigation of the impact of the annealing conditions and fabrication processing was undertaken. It was found that the cleaning stages of the fabrication had a significant impact on the resulting morphology of the GaN after thermal etching. In all three cases, sites arguably suitable to house site-controlled quantum dots were achieved.

Finally, site-controlled GaN quantum dot growth was attempted on the AlN nanostructures developed. Whilst the growth of site-controlled quantum dots at the specifically targeted regions of the nanostructures wasn't achieved, it is certainly arguable that there was site-controlled quantum dot growth in other regions of the nanostructures.

III-N SCQDs hold immense promise to further advance QIS technology at temperature achievable by thermoelectric cooling or even room temperature. Further development of the field could lead to the realisation of more practical QIS devices that could become far more ubiquitous in everyday life and technology. Thus, III-N SCQDs present an exciting field of present day and future research.
Date of Award12 Dec 2022
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorPhilip Shields (Supervisor) & Daniel Wolverson (Supervisor)


  • III-N
  • Quantum Dots
  • III-N Nanostructures
  • AlN Nanostructures
  • Sublimation of GaN

Cite this