UK’s CSC-led GaNTT consortium awarded £1.3m via the Office for Low Emission Vehicles

A consortium led by the Compound Semiconductor Centre Ltd (CSC) - a joint venture founded in 2015 between Cardiff University and epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK - has been awarded £1.3m in funding through ‘The road to zero emission vehicles’ competition sponsored by OLEV (the Office for Low Emission Vehicles). CSC leads a consortium of partners across the power electronics supply chain: SPTS Technologies Ltd of Newport, Wales; Newport Wafer Fab Ltd; Turbo Power Systems Ltd of Gateshead, UK; and the South Wales-based Compound Semiconductor Applications (CSA) Catapult, supplemented with academic expertise in power systems and devices at Swansea University and Coventry University.

The project GaNTT (Realisation of a mass-manufacturable Vertical GaN Trench FET architecture) will develop a voltage-scalable, vertical gallium nitride process platform (200-600V) suitable for electric vehicle (EV) applications and integrate the resulting device into an on-vehicle demonstrator for bi-directional battery charging. Vertical GaN architectures are a viable future technology for low- to medium-voltage and power applications, e.g. on-board charging (OBC) and DC-DC applications where higher switching speed is desirable. It also has the potential to meet the cost challenges related to existing silicon cabide (SiC) field-effect transistor (FET) technologies, although significant challenges in epitaxial material layer quality and device thermal management require de-risking.

The project will focus on the development of large-diameter substrate solutions that provide high-quality, thick GaN layers and address the challenges of lattice mismatch and wafer bow by employing novel epitaxial substrate solutions for future foundry products. Vertical GaN devices architectures enable FET operation at high electric fields and thus facilitate a significant reduction in chip area compared with lateral power devices. The breakdown voltage can be increased by increasing the thickness of the epitaxial drift region supporting the electric field, enabling the voltage to be scaled independently of chip area. The device approach also incorporates an innovative source-metal/P-body Schottky contact approach, patented by researchers at Swansea and Coventry Universities, to provide better control and stability of the channel threshold voltage.

Crucially, the project will evaluate prototype devices at the packaged device and sub-system level, with Turbo Power Systems providing a tier-1 automotive testing environment. The activity aims to establish a ‘materials to system’ UK supply chain in wide-bandgap materials and enhance exploitation opportunities for all partners by ensuring that device development is driven by automotive requirements. The performance benefits of the new platform technology are not limited to automotive applications, but are also suitable for use in other harsh environments (e.g. space applications, where the combination of improved power density and radiation-hardness would reduce payload and improve system reliability).

“Vertical GaN Power Technology will deliver emerging opportunities across a broad applications space, currently growing at >50% CAGR [compound annual growth rate] and forecast to be worth >$150-300m by 2023,” says CSC’s GaN programme manager Robert Harper. “This activity will build on UK strengths in compound semiconductor materials and device technology to energize a new supply chain in automotive power component supply,” he adds.

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