Technical consultants Ryan Maughan is an award-winning engineer and business leader with more than 20 years’ experience in the High-Performance, Heavy-Duty and Off-Highway Automotive markets. Prominent in the development of Power Electronics, Electric Motors and Drives (PEMD) for these demanding applications, he has successfully founded, scaled and exited three businesses in the electric vehicle space. He is currently CEO of eTech49 Limited, an advisory business specialising in disruptive hardware technology in PEMD. In addition, he is Chairman of EV North, an industry group representing the booming EV industry in the north of England, a board member of the North East LEP and an adviser to a number of corporations. Danson Joseph has had a varied career in the electrical power industry, having worked in areas ranging from systems engineering of photovoltaic powerplants to developing the battery packs for Jaguar Land Rover’s I-Pace SUV. With a PhD in electrical machines from the University of Witwatersrand in South Africa, Danson has focused on developing battery systems for automotive use. After completing the I-Pace project he formed Danecca, a battery development company with a focus on prototyping and small-scale production work, as well as testing and verifying cells and packs destined for mass production. Dr Nabeel Shirazee graduated from Leicester University in 1990, where he studied electrical and electronic engineering. An MSc in magnetic engineering followed at Cardiff University, where he continued his studies, earning a PhD and developing a permanent magnetic lifting system that has been patented by the university. His interest in magnetics led to a patented magnetic levitation system that was awarded the World’s No 1 Invention prize at INPEX in the USA. In 1999, he founded Electronica, a magnetics research and design consultancy. Since then, he has been involved in various projects, including the design of an actuator motor for a British aerospace company. He has also licensed the levitation technology in France. Ryan Maughan Danson Joseph The Grid 11 Memory device functions at 600 C Researchers in the USA have developed a heat-resistant, non-volatile memory device able to withstand temperatures of over 600 C, writes Nick Flaherty. The ferroelectric aluminium scandium nitride (AlScN) device can be used in electric aircraft and motors to add machine-learning controls and sensors in harsh environments. Deep Jariwala and Roy Olsson of the University of Pennsylvania, and their teams at the School of Engineering and Applied Science, demonstrated that the memory technology is capable of enduring temperatures up to 600 C – more than twice the tolerance of any commercial drives on the market – and these characteristics were maintained for more than 60 hours. “Our high-temperature memory devices could lead to advanced computing where other electronics and memory devices would falter,” says Jariwala. “This isn’t just about improving devices – it’s about enabling new frontiers in science and technology.” “AlScN’s crystal structure gives it notably more stable and strong bonds between atoms, meaning it’s not just heat-resistant but also pretty durable,” says researcher Dhiren Pradhan. “But, more notably, our memory device design and properties allow for fast switching between electrical states, which is crucial for writing and reading data at high speed.” The memory device consists of a metal-insulator-metal structure, incorporating nickel and platinum electrodes with a 45 nm layer of AlScN. This thickness is a key consideration as particles move more erratically at elevated temperatures. “If it is too thin, the increased activity can drive diffusion and degrade a material. If too thick, there goes the ferroelectric switching we were looking for, since the switching voltage scales with thickness and there is a limitation to that in practical operating environments. So, my lab and Roy Olsson’s lab worked together for months to find this Goldilocks thickness,” says Jariwala. The devices were grown on 4 in diameter silicon wafers, and exhibit clear ferroelectric switching up to 600C with distinct on/off states. At 600C, the devices exhibit one million read cycles and readable on/off ratios for over 60h. The operating voltages of the AlScN ferrodiodes are less than 15V at 600C, making them compatible with hightemperature, silicon-carbide devices, which are also used in inverters. “Conventional devices using small, silicon transistors have a tough time working in high-temperature environments – a limitation that restricts silicon processors – so, instead, silicon carbide is used,” says Jariwala. “While silicon-carbide technology is great, it is nowhere close to the processing power of silicon processors, so advanced processing and data-heavy computing such as AI can’t really be done in high temperatures or any harsh environments. “The stability of our memory device could allow integration of memory and processing more closely together, enhancing speed, complexity and efficiency of computing. We call this ‘memory-enhanced compute’ and are working with other teams to set the stage for AI in new environments,” he adds. ELECTRONICS E-Mobility Engineering | July/August 2024 The memory technology is capable of enduring temperatures up to 600 C 12 The Grid TRANSISTORS Testing gallium nitride power at high temperatures Researchers in the USA are finding a way to use gallium nitride (GaN) power devices at high temperatures, writes Nick Flaherty. A team at the Massachusetts Institute of Technology (MIT) is investigating the impact of temperature on ohmic contacts in a gallium nitride device. The team found extreme temperatures did not cause significant degradation to the gallium nitride material or contacts, and found they were structurally intact when held at 500 C for 48 hours. Understanding how contacts perform at extreme temperatures is a key step in developing high-performance transistors. “Transistors are the heart of most modern electronics, but we didn’t want to jump straight into making a gallium nitride transistor because so much could go wrong. We first wanted to make sure the material and contacts could survive, and figure out how much they change as you increase the temperature. We will design our transistor from these basic material building blocks,” says researcher John Niroula. “No one has really studied what happens when you go all the way up to 500o.” The team added ohmic contacts to GaN devices using the two most common methods. The first involves depositing metal onto the gallium nitride and heating it to 825 C for about 30 seconds to anneal the metal. The second involves removing chunks of gallium nitride and using a hightemperature technology to regrow highly doped gallium nitride in its place. “Contacts made with both methods seemed remarkably stable,” says Niroula. July/August 2024 | E-Mobility Engineering
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