Non-volatile memristors as prospective radio frequency switches for 6G communications - A review

As communication technologies continue to improve to the 6G standard, highly performing radio frequency (RF) switches that have short switching times, high energy efficiency, high cutoff frequencies, capabilities of operating beyond 100 GHz while maintaining reasonable RF performance, and high data transmission rates of 100 Gbit s^-1 are needed. Existing RF switches based on solid-state and microelectromechanical systems (MEMS) technologies fall short of meeting these requirements because of their volatility and parasitic inductive effects that lead to undesirably high insertion losses at high frequencies. Non-volatile memristors are emerging as likely candidates to replace traditional switches. They offer numerous benefits, including virtually zero static energy consumption, fast switching speeds, and excellent scalability. This review will provide an overview of the progress and challenges associated with implementing four types of non-volatile memristive technologies as RF switches: Resistive random access memory (ReRAM), conductive bridge random access memory (CBRAM), phase change memory (PCM), and memory based on two-dimensional (2D) materials, specifically molybdenum disulfide (MoS₂) and hexagonal boron nitride (hBN). The performance of these prospective switches is compared against one another and subsequently benchmarked against existing switch technologies. The review will provide an objective critique of the future readiness for 6G for the four main types of memristive switch technologies based on factors such as RF performance, CMOS compatibility, and fabrication maturity. Special attention is paid to 2D material-based memristors involving MoS₂ and hBN, which have attracted significant research interest for multiple benefits that are claimed to be distinctive. Finally, it will also propose research directions to further the progress of future memristive RF switches.