A team at the Department of Electronic and Computer Engineering at the Hong Kong University of Science and Technology (HKUST) has developed a complete set of complementary GaN logic including NAND and NOR gates and the transmission gate for the first time.
The work, published in the journal Nature, also includes details of a monolithic integration process to build GaN logic circuits that can be integrated with GaN power switching devices. With monolithic integration, the parasitic inductances induced by interconnections between power devices and off-chip peripheral circuits could be eliminated to enable high switching frequency, lower losses and smaller power converter designs.
Development of complementary GaN circuits has been hindered by the difficulties in implementing p-channel transistors and integrating them with complementary n-channel ones. So the team, led by Prof. Kevin Chen, developed a new approach to tackle the challenges of the gate-dielectric/channel interface. They engineered a buried channel structure enabled by an oxygen plasma treatment (OPT) technique to build a p-channel GaN transistors with well-balanced performance matrix of threshold voltage for enhancement-mode operation, high ON/OFF current ratio, and high current driving capability.
The team has also demonstrated multiple-stage logic circuits that can be operated at megahertz frequencies.
“This is an exciting leap forward. We have first proven that all building blocks are functional, then these building blocks could be put together for more complicated entities. Therefore, any GaN-based complementary logic circuits can be constructed by making combinations of these logic gates,” said Chen.
The technology is particularly aimed at computing/control electronics for harsh environments such as in automotive and aviation systems as well as integrated control, sensing, protection, and drive functions alongside basic power switching functions.
In the near-medium future, it becomes feasible to build GaN computing chips for critical missions such as planetary and deep space explorations on 250 and 180nm processes says Chen.
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