Research
Theory and multi-scale simulation of emerging semiconductor materials for photonic, electronic and photovoltaic applications.
Overview
Our work develops the theory of novel and emerging semiconductor material systems, with the aim of delivering enhanced performance and new capabilities in next-generation semiconductor technologies. The overarching theme is to build key insights obtained from atomistic electronic structure calculations into atomistic and continuum empirical models, enabling quantitative prediction of technologically relevant properties of semiconductor materials and nanostructures.
In practice this spans first-principles calculations of fundamental material properties, the derivation and parametrisation of empirical models for multi-scale simulation, software implementations of those models, and in silico design of semiconductor nanostructures for device applications.
Research themes
Click a theme to expand.
Emerging semiconductor alloys
Highly-mismatched alloys - dilute bismides and dilute nitrides - and direct-gap group-IV alloys such as GeSn and SiGeSn offer band structures that cannot be reached with conventional semiconductors. Their properties depend strongly and non-linearly on composition, driven by resonant interactions between localised impurity states and the extended states of the host matrix, and by alloy disorder and short-range ordering.
We quantify these effects using first-principles calculations, and distil them into models - band-anticrossing, tight-binding and pseudopotential - accurate enough to predict the properties that matter for devices.
Crystal phase engineering
Advances in growth now allow established cubic semiconductors to be stabilised in metastable hexagonal crystal phases. This emerging paradigm offers a route to re-engineer the properties of well-understood materials - including, in some cases, converting an indirect-gap material to a direct-gap one.
We compute the electronic and optical properties of these phases from first principles, and analyse “crystal phase heterostructures” formed by alternating cubic and hexagonal segments within a single material. This theme grew out of the SATORI Marie Skłodowska-Curie Global Fellowship.
Quantum nanostructure design
Material properties only become device performance once they are embedded in a nanostructure. We design quantum wells, superlattices and related heterostructures in silico, computing confined state energies, optical matrix elements, and the radiative, Auger and defect-mediated recombination rates that set efficiency limits in lasers, LEDs, detectors and photovoltaic cells.
The aim throughout is quantitative prediction: identifying the compositions, strains and layer geometries that deliver a target performance, before anything is grown.
Model and software development
Bridging length scales is the practical bottleneck in semiconductor theory: first-principles methods are quantitative but limited in system size, while continuum models are cheap but only as good as their parameters. We derive and parametrise multi-band k·p Hamiltonians, tight-binding models and empirical pseudopotentials directly against first-principles reference calculations, so that nanostructure-scale simulations retain ab initio accuracy.
These models are released as open-source software wherever possible - see the Software page.
Funded projects
Current and recent research funding.
Royal Society-Research Ireland University Research Fellowship
Boilerplate - add the project title, a two-line summary and the award reference here.
SATORI (MSCA Global Fellowship)
Semiconductor crystal phase engineering: new platforms for future photonics. A three-year Marie Skłodowska-Curie Individual (Global) Fellowship, with a two-year outgoing phase at UC Santa Barbara and a reintegration phase at Tyndall.
Project on CORDIS →Data management plan (PDF) →
NUI Postdoctoral Fellowship in the Sciences
Theory and multi-scale simulation of the electronic, optical and transport properties of direct-gap group-IV semiconductor alloys.