Applications are invited for a four-year Ph.D. studentship in theoretical and computational condensed matter physics at the School of Physics, University College Cork (UCC), under the supervision of Dr. Christopher Broderick. The studentship is funded by a recently awarded Royal Society-Science Foundation Ireland University Research Fellowship, includes a stipend of €22,000 per annum, and pays full tuition fees. The preferred start date is September 2024, or as soon as possible thereafter.

The research project centres on the theory and in silico design of heterostructured semiconductor nanowires (NWs), to identify and optimise targeted optical and electrical properties underpinning potential applications spanning a range of classical and quantum photonic and electronic device technologies.

Two classes of NW heterostructures are of interest: (i) radial “core-shell” heterostructures in which the material composition is varied in the direction perpendicular to the NW axis, especially core-shell NWs based on direct-gap group-IV alloys including GeSn, and (ii) axial “polytype” heterostructures formed by alternating the crystal structure of a given group-IV or III-V material between its stable cubic (diamond or zinc blende) phase and its metastable hexagonal (lonsdaleite or wurtzite) phase, especially polytype NWs based on direct-gap lonsdaleite group-IV SiGe alloys and on direct-gap wurtzite III-P alloys. NW heterostructures of type (i) are of interest for the development of efficient infrared-wavelength light emitters for integrated Si photonics.  NW heterostructures of type (ii) are of interest for the development of novel Si-compatible transistor architectures, for applications in integrated Si photonics, and to address the so-called “green-gap” for visible-wavelength emitters in solid-state lighting and display technologies.

Developing quantitative understanding of the properties and performance of photonic and electronic devices based on these nanostructures mandates, in the first instance, developing predictive atomistic quantum mechanical calculations of the NW properties. Beginning from first principles calculations based on density functional theory, the student will develop transferable interatomic potentials and model Hamiltonians that allow to accurately describe the fundamental properties of both the cubic and hexagonal phases of group-IV and III-V semiconductor materials. These models will enable accurate large-scale atomistic electronic structure calculations for NW heterostructures, providing input to develop predictive calculations of key properties relevant to device applications (e.g. radiative and non-radiative carrier recombination rates for applications in NW-based photonic devices). The results of these calculations will then guide in silico optimisation of candidate heterostructures for targeted device applications.

The project will encompass a combination of model development and parametrisation, software development, and high-performance computing. The outcome of the project will constitute a new state-of-the-art in the understanding of the fundamental properties of heterostructured semiconductor NWs, and provide guidance to material growers and device engineers working on novel material concepts to deliver enhanced performance and new capabilities in next-generation semiconductor devices.

The project will empower the student to develop a range of analytical, computational and transferable skills which, at the conclusion of the Ph.D., will place them in a competitive position to undertake postdoctoral research or to obtain a high-value position in industry.