Strained germanium photonic crystal membranes for scalable and efficient silicon-based photonic devices
Lead Research Organisation:
University of Surrey
Department Name: ATI Physics
Abstract
Silicon is ubiquitous for electronics and the most widely exploited semiconductor in the world available in plentiful and cheap supply. In spite of its success in electronics, silicon is fundamentally limited in terms of its ability to produce light. This is due to its so-called indirect band gap which means that electrons cannot easily lose energy by producing photons. In contrast, in direct band gap compound semiconductors such as GaAs and InP electrons can very easily lose energy resulting in the production of photons. Consequently, such semiconductors are widely exploited in light emitters including lasers and light emitting diodes. However, compound semiconductors are much more expensive to produce. Hence there is a strong desire to be able to produce optically-efficient direct band gap semiconductors on a silicon-based platform.
This project aims to resolve this fundamental constraint by develop an entirely new approach to fabricating direct band gap germanium layers on silicon. Germanium can be readily grown on silicon and has a band gap that is much closer to being direct. It has been theoretically predicted that by straining the germanium crystal by >2% (tensile), it will become a direct band gap semiconductor. Producing stable highly strained germanium layers has proven to be technologically challenging. We will overcome this challenge using our recently discovered ion-implantation method to generate stable high tensile strained germanium layers. Such layers offer the potential to achieve record optical efficiencies in germanium. Using these layers we will demonstrate optical gain and lasing in photonic crystal nanocavities in the mid-infrared using an all group-IV based system. This combination of electronic- and photonic band structure and strain engineering offers a step-change in developing lasers on silicon with strong exploitation potential to scale-up and transform sensors for medical, environmental and industrial applications.
This project aims to resolve this fundamental constraint by develop an entirely new approach to fabricating direct band gap germanium layers on silicon. Germanium can be readily grown on silicon and has a band gap that is much closer to being direct. It has been theoretically predicted that by straining the germanium crystal by >2% (tensile), it will become a direct band gap semiconductor. Producing stable highly strained germanium layers has proven to be technologically challenging. We will overcome this challenge using our recently discovered ion-implantation method to generate stable high tensile strained germanium layers. Such layers offer the potential to achieve record optical efficiencies in germanium. Using these layers we will demonstrate optical gain and lasing in photonic crystal nanocavities in the mid-infrared using an all group-IV based system. This combination of electronic- and photonic band structure and strain engineering offers a step-change in developing lasers on silicon with strong exploitation potential to scale-up and transform sensors for medical, environmental and industrial applications.
Publications
Fitch C
(2022)
Carrier Recombination Properties of Low-Threshold 1.3 µm Quantum Dot Lasers on Silicon
in IEEE Journal of Selected Topics in Quantum Electronics
Fitch C
(2022)
Refractive index dispersion of BGa(As)P alloys in the near-infrared for III-V laser integration on silicon
in Journal of Applied Physics
Description | Silson Ltd |
Organisation | Silson Ltd |
Country | United Kingdom |
Sector | Private |
PI Contribution | Our research team worked with Silson to help develop new materials (Ge and GeSn alloys and heterostructure) to develop into membranes for photonic and electronic applications. Our team brought expertise in semiconductor materials, materials processing and device applications. |
Collaborator Contribution | Silson have develop process capabilities to produce thin suspended membranes that we are using in the project to demonstrate direct band gap group IV materials. The eventual aim is to demonstrate devices such as lasers. |
Impact | The collaboration includes expertise in physics, materials science, chemistry and engineering. |
Start Year | 2021 |
Description | UCL |
Organisation | University College London |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | The aim of this collaboration is to help develop the growth of group IV alloys such as GeSn using Molecular Beam Epitaxy. Our input has been on the development of layer designs and structural and optical characterisation of the material to provide feedback to the growth team at UCL to help improve the material with the aim to produce photonic and electronic devices. |
Collaborator Contribution | The team at UCL has developed improvements in the understanding of how novel group IV alloys can be grown using MBE. This is important to develop the base materials that we are using to demonstrate membrane-based photonic devices on silicon. |
Impact | The output thus far has focused on an improved understanding of group IV alloys grown using MBE. |
Start Year | 2021 |