The UK’s Engineering and Physical Sciences Research Council (EPSRC) has awarded funding totaling more than £823,800m to two universities for the project ‘Novel High Thermal Conductivity Substrates for GaN Electronics: Thermal Innovation’ (from 1 May 2013 to 30 April 2016).
A £430,597 grant (EPSRC reference EP/K024337/1) goes to the University of Bath’s Department of Electronic and Electrical Engineering, with principal investigator Dr DWE Allsopp joined by professor W Wang as the other investigator.
A £393,218 grant (EPSRC reference EP/K024345/1) goes to the University of Bristol’s Department of Physics, with principal investigator professor M Kuball joined by professor D Cherns as the other investigator. Bristol’s project partners are IQE Silicon Compounds Ltd, NXP Semiconductors UK Ltd and Plessey Semiconductors Ltd.
In their grant application, the researchers say that AlGaN/GaN high-electron-mobility transistors (HEMTs) are a key enabling technology for future power conditioning applications in the low-carbon economy, as well as for both high-efficiency military and civilian microwave and RF systems.
Although the performance of AlGaN/GaN HEMTs currently reaches RF powers of up to 40W/mm at frequencies exceeding 300GHz, their long-term reliability, which is often thermally limited, is still a serious issue, not only in the UK and Europe but also in the USA and Japan. Corresponding challenges exist for power conditioning applications.
To mitigate the existing thermal device challenges, the aim of the project is innovation and step change in thermal management of AlGaN/GaN HEMT devices by developing novel substrates, in particular (1) high-value substrates that have higher heat extraction capability than high-cost silicon carbide (SiC) substrates commonly used for GaN RF applications, and (2) low-cost substrates that have improved heat extraction capability to gallium nitride on silicon (GaN-on-Si) substrates for more cost-sensitive power electronics markets. The resulting step-change in improvement in heat spreading should improve reliability, circuit efficiency and ease system constraints of GaN electronics, it is reckoned. To enable optimization of thermal substrate properties, key enabling new thermal analysis technologies will be developed.
The UK has roadmaps for employing RF and microwave GaN electronics in defence as well as satellite communication. Key UK industrial players in this field include Selex, MBDA, and Astrium, all requiring reliable and efficient GaN RF and microwave electronics, which the project aims to enable via the new heat-extracting substrate technologies and improved thermal characterization methods. IQE UK, which is supporting the project, is a key component in the supply chain for RF GaN applications.
The corresponding roadmap for power electronics requires cost-effective GaN power devices on silicon substrates, with UK-based manufacture at project partner NXP as well as International Rectifier (IR).
Further business opportunities are expected to emerge through development of the substrate itself (e.g. via Element-6), at IQE through the development of III-nitride epitaxial growth for optimum heat extraction, or through spin-out companies.
