ECCS-EPSRC - Advanced III-N Devices and Circuit Architectures for mm-Wave Future-Generation Wireless Communications'

Ubiquitous, high-performance communication is the backbone of our society, and promises to play an increasing role not only in individual's daily lives, but just as importantly in the background with communication among devices (e.g. vehicle-to-infrastructure for mobility, process control and monitoring in industrial and manufacturing, virtualization of full environments for the metaverse, among others). The resulting explosion in data that must be processed and communicated requires extraordinary bandwidth and network ubiquity, which in turn demands supporting electronics that is high performance, power efficient, and low cost. This EPSRC - NSF proposal targets a great leap forward in the most critical link, the wireless power amplifier, that is essential to realizing a vision of ubiquitous, high-speed, transparent mobile communication.

Power amplifiers are among the most critical elements in any communication system as they dictates the overall efficiency of the system. GaN-based HEMTs are especially promising for high-performance power amplifiers, but current GaN-based systems suffer from limited frequency coverage, efficiency and linearity due to a combination of factors, including device design e.g. use of field plates effectively limits operation to 30 GHz and below, and materials issues e.g. deep level traps, self-heating means that gain and efficiency degrade rapidly both with output power as well as frequency.

We leverage in this programme transformative advances in both GaN-based transistor design and novel circuit topologies to dramatically improve the efficiency, bandwidth, linearity, and cost of the key wireless elements of a communication system, through co-design. The technology is based on polarization-engineeered graded channel GaN HEMTs that show a substantial improvement in linearity in comparison to conventional HEMTs. By combining with thorough investigation of their underlying device physics including trap states and thermal management, we address major effects that degrade the performance of GaN at increasing frequencies (i.e. Ka band up to 40 GHz) by optimizing device design and fabrication. We will design harmonically terminated amplifiers based on our new class of contiguous modes, that allow designers wider choice of impedances for desired characteristics of efficiency, linearity and output power.

The project brings together world leading experts in the Universities of Notre Dame, Bristol and Sheffield, working alongside supporting industry in UK and US, that completes the entire supply chain from substrate growers, device/chip fabrication to circuit designer in both countries. The targeted enabling millimetre-wave communication technology is expected to be the next frontier in emerging applications that play a critical role in the levelling up agenda to drive prosperity in all regions of the UK, the US and worldwide. For example 5G is expected to underpin new industries worth $13.2T in goods and services in the UK alone by 2035.