A Semi-floating Body Memory Featuring Brain-like Behaviors

Innovating electronic devices to mimic human brain behaviors has been a long-standing desire. (Mehonic, A., Kenyon, A. J. Brain-inspired computing needs a master plan. Nature 2022, 604, 255-260 and Mead, C. Neuromorphic electronic systems. Proceedings of the IEEE 1990, 78, 1629-1636). Here, we present a semi-floating body memory (SFBM) exhibiting various human brain-like memory behaviors. The SFBM is designed similarly to a p-type silicon-on-insulator (SOI) MOSFET, except that a metal/graphene/silicon overlapping heterojunction is formed close to the drain. The proper operation of device terminal bias voltages introduces and modulates the impact ionization (II) at the heterojunction interface and forms an ungated semi-floating body underneath for charge storage, further enabling multiple unique memory behaviors. The SFBM achieves a fresh retention time of ∼1 h, 300× that of the conventional floating body memory. Importantly, the retention time is extended to over a day by the read operation, precisely mimicking the revisitation behavior of human memory. In addition, the SFBM responds to a 20 ns write pulse in a few seconds, and it mimics the shocking behavior of the human brain in response to a very fast and strong stimulus.(Kim, J. J. & Fanselow, M. S. Modality-Specific Retrograde Amnesia of Fear. Science 1992, 256, 675-677 and Brewin, C. R. Memory and Forgetting. Current Psychiatry Reports 2018, 20, 87). Finally, the back gate control of the SFBM enables real-time quantification of the device current up to 4 orders of magnitude; this resembles the hormone regulation of synaptic weights in the human brain. All these brain-like features position the SFBM as a strong candidate for brain-inspired computing units, and a 1T-1S content-addressable memory (CAM) cell is experimentally demonstrated using a minimum number of transistors for future compute-in-memory (CIM) purposes.