Speaker: Prof. Giorgos Fagas, Director of Strategic Development, Tyndall.

Title: "GeSn: a group-IV materials platform for quantum devices"

Date: Monday, November 10, 2025 - Time: 11 AM

Venue: CeNSE Seminar Hall

Abstract:

There are several proposed platforms for realising quantum devices and more specifically 
qubits, the basic units of quantum information processing, to perform quantum computation. 
While there has been great scientific progress and proof-of-concept demonstrations on all 
these platforms, to address the challenge of scalability it makes sense to use all the 
machinery of traditional semiconductors. For example, charge or spin-qubits can be realised
 by using gate-defined quantum dots (QDs) in semiconductors in a similar fashion to the 
processes used in CMOS for conventional field-effect transistors (FETs) or state-of-the-art 
finFET technology. In the last few years, Ge has progressed immensely from a conceptually 
new material for qubits to demonstrations of two-qubit logic and most recently the first 
demonstration of a four-qubit quantum processor. Furthermore, the GeSn alloy is a material 
platform that carries the promise of highly desirable extreme mobility, low effective mass 
and added optical control for the qubit manipulation.

In this talk, I will provide an overview of the recent developments of Ge-based platforms 
such as epi-grown and strained Ge and GeSn layers on Si for hosting hole-based qubits, 
and further discuss challenges related to Ge processing modes for realising qubit devices. 
The device architectures we discuss are analogous to conventional planar and fin-FET 
devices with enlarged number of gates controlling the definition of the quantum dots 
in the Ge/GeSn channel. The processing modes are related to the use of electron beam 
lithography (EBL), reactive ion etching (RIE) and atomic layer deposition (ALD) of gate 
materials (gate oxide and TiN metal). The aim is to understand high fidelity/resolution 
gates patterning, as well as various surface passivation (pre-treatments) for the ALD 
gate oxides (AlOx, HfO and ZrOx) formation, the quality of the interfaces and dielectrics used. 
Finally, I will discuss the application of the GeSn materials platform as a highly sensitive 
charge sensor in a single-electron transistor (SET) configuration.

Biography:

Professor Giorgos Fagas (PhD, MBA) serves as the Director of Strategic Development at 
the Tyndall National Institute and is a member of its Executive Leadership team. In this 
capacity, he is responsible for shaping the institute's overall international positioning, 
initiating and overseeing major strategic initiatives that span the entire institute, and 
managing the collective strategic planning process. Giorgos also ensures the effective delivery
 of Tyndall's strategic plan, driving the institute towards its long-term objectives.

A key part of Giorgos’s remit is Tyndall’s international profile. He is actively involved in 
several influential policy and industry groups, both within Ireland and across Europe. These 
include serving as the Europe Chair for the Industry Association for Microelectronics and 
Electronic Systems Design in Ireland (MIDAS), holding a directorship at the SiNANO Institute, 
and being a member of the Executive Committee of EPoSS and the AENEAS Scientific Council. His 
academic contributions extend globally as well, holding an adjunct professorship at the Centre 
for Nanoscience and Engineering (CeNSE) at the Indian Institute of Science (IISc).

Giorgos holds a PhD in Physics from Lancaster University, UK, awarded in 2000, and an executive 
MBA from University College Cork, Ireland, completed in 2012. Previously, Giorgos led the CMOS++ 
programme at Tyndall, which comprised around 50 researchers. This strategic programme focused on 
emerging materials, devices, and architectures for next-generation information processing, 
particularly in relation to interfacing with CMOS technology and exploring possibilities beyond it. 
His own research group, the Quantum Electronic Device Group (QED), is highly interdisciplinary, 
combining expertise from physics, chemistry, materials science, electrical engineering, and 
theoretical modelling and simulation. The group’s aim is to engineer emerging material platforms 
and develop new devices for scalable quantum computer architectures.

Giorgos has played a significant role in aligning and securing resources for the launch and 
sustainability of the Tyndall Quantum Computer Engineering Centre, the first dedicated programme 
of its kind in Ireland aimed at advancing quantum science. He has also led Tyndall’s successful 
involvement in the Tier 1 Pilot Lines NanoIC and FAMES, supporting the EU Chips Act, from initial 
negotiations through to project kick-off and execution.

Instrumental in the development of the 'Quantum 2030 National Strategy for Quantum Technologies', 
Giorgos continues to participate in its implementation group and chairs the activities of the 
‘National and International Collaboration’ Pillar, supporting the strategy’s effective execution.

Giorgos is a key contributor to major international strategic research and innovation agendas, 
including the ECS-SRIA and IRDS. He has initiated several EU projects, acting as Principal 
Investigator on 18 occasions and as Coordinator on three. Notably, he has led EU-funded 
programmes such as ASCENT+ and INFRACHIP, which provided open access to infrastructure for 
early-stage research on nanoelectronics and semiconductor chips, and has overseen the ICOS-project
 activity on Technology Scanning and Foresight, focused on international cooperation in semiconductors.

Host Faculty: Prof. Gayathri Pillai