Monolithic On-chip Integration of Electronics & Photonics Using III-nitrides for Telecoms

Internet and telecoms are facing an explosive growth in data traffic, increasing at 50% per year. This requires the development of monolithic on-chip integration of electronics and photonics, which offers a massive reduction in both footprint and processing costs. Such a compact system will require a high power density and excellent high temperature tolerance. Monolithically integrating III-nitride based electronics and photonics on silicon on a single chip will represent the most promising approach to meeting the requirements in the telecoms regime. The photonic parts include active (laser diodes) and passive (photodetectors) components linked by waveguides, where the laser diodes are controlled by high electron mobility transistors. The electronic and photonic parts both need to meet the requirements for high power, high frequency and high temperature operation, as well as excellent temperature stability and robust mechanical properties. Conventional III-V semiconductors (GaAs or InP) suffer a number of fundamental limitations such as intolerance to high-temperatures, temperature sensitivity, limited power density capacity and fragility. They also exhibit high losses due to scattering (high refractive index) and multiphoton absorption. III-nitride semiconductors all have direct bandgaps and cover a vast spectral region from deep ultraviolet to infrared. Compared with conventional III-V materials, the III-nitrides exhibit major advantages in the fabrication of high power, high frequency and high temperature devices due to their intrinsically high breakdown voltage, high saturation electron velocity and excellent mechanical hardness. III-nitrides exhibit low free carrier absorption, negligible multiphoton absorption, low refractive index (2.3 for GaN compared with 3.5 for GaAs) and superior temperature stability of the refractive index (one order of magnitude higher than that of InP). Therefore, III-nitrides offer great potential to revolutionise current internet and telecoms and enable ultra-fast speed and ultra-broad bandwidths, going far beyond that so-far achieved in the telecoms regime (1.3-1.55 um). Up to now research on III-nitrides has mainly been confined to the visible spectral range but this is not a limit. III-nitrides based devices exhibit superior properties in terms of delivering the power/efficiency required for next-generation telecoms. This is important to the communications industry, which is expected to use 20% of the global electricity by 2025, where a large proportion (>30%) is consumed by the data centre cooling systems. Monolithically integrating III-nitride electronics and photonics on silicon on a single chip by direct epitaxy in the telecoms regime would therefore offer transformative performance.

Our ambitious vision is to employ the two major leading epitaxial growth techniques (MOVPE and MBE) for III-nitrides, combining the leading-expertise established at Sheffield, Cardiff and Strathclyde along with a world-leading research team at Michigan in USA in order to demonstrate the first monolithic on-chip integration of III-nitride based electronics and photonics on silicon with operation in the telecoms regime. This is expected to revolutionise current internet and telecoms.

Explosive growth in data traffic requires the development of monolithic on-chip integration of electronics and photonics, which offers a massive reduction in both footprint and processing costs. Such a compact system will require a high power density and excellent high temperature tolerance. Therefore, monolithically integrating III-nitride with silicon on a single chip will represent the most promising approach to meeting the requirements in the telecoms regime. The emerging 5G systems including RF and power electronic components will be dominated by GaN transistors. Therefore, the development of III-nitrides on silicon for on-chip integration of electronics and photonics has the potential to benefit society by contributing to wealth creation and economic prosperity.

All the involved universities strongly support knowledge-transfer. The technologies developed will be protected through patents, non-disclosure agreements and appropriate industrial partners sought to develop any breakthroughs into commercial products. The applicants have wide experience of collaboration with the semiconductor industry, and have a strong track record, for example the establishment of Seren Photonics Ltd based on the Sheffield team's research innovations. Strathclyde has many successes in working with multinational companies and Catapult Centres (with at least 4 connected to its Technology and Innovation Centre (TIC) also containing the UK's only Fraunhofer Centre). The Compound Semiconductor Centre (CSC) is a joint venture between Cardiff University and IQE plc founded in 2015 aiming to underpin the creation of a unique global capability for emerging 21st century technologies based on Compound Semiconductor materials. CSC and their partners IQE have an established Open Innovation programme, which will be a vehicle for dissemination and exploitation for the outputs of this project. Further impact on industry can be made through regular communications established with a number of companies in the UK, such as Dynex Semiconductor; Cambridge GaN Devices; Plessey; Experior Micro Technologies Ltd; LIA, etc.

The project will impact a wide range of academic areas in the field of III-nitrides and other III-Vs. Advances achieved through this project will provide new collaborative opportunities including bids for further funding. Academic impact will also be realised through the UK Nitride Consortium (UKNC), which has 150+ members from industry and academy. Prof Martin is the chair of the UKNC. Sheffield is host to the EPSPS National Epitaxial Facility (NEF) which has a remit to supply device quality material to the UK Scientific Community and develop new technologies. Prof Martin is the chair of the NEF steering committee. The training provided for the project's junior researchers will also have a direct economic impact via the provision of skilled workers. The project will contribute to the pool of staff trained in leading compound semiconductor device fabrication/ design/characterisation, critical requirements in maintaining the competitive edge of UK companies. The Sheffield team organised the very successful 2012 summer school on III-nitrides, attracting > 40 Ph.D students and junior researchers from both academia and industry across the UK. We plan to build on this success and organise a summer school during the project. Plans for education and outreach include the development of hands-on activities to be presented to teams of teachers and students and at University Open Days and Science Centres. The project team will also contribute to public engagement activities, such as Strathclyde's EU-funded "Explorathon" and "Images of Research" exhibition; accepting A-level students from local schools for working experience which was very successful at Sheffield; developing "elevator pitches" which has been tested at Cardiff via a series of visits by a number of politicians.