Spin-Orbit-Torque Field-Effect Transistor (SOTFET): A New Magnetoelectric Memory*

Spin-based memories are attractive for their non-volatility and high durability but provide modest resistance changes, whereas semiconductor logic transistors are capable of large resistance changes but lack memory function with high durability. The recent availability of multiferroic materials provides an opportunity to directly couple the change in spin states of a magnetic memory to a charge change in a semiconductor transistor. In this work, we propose and analyze the spin-orbit-torque field-effect transistor (SOTFET), a device with the potential to significantly boost the energy efficiency of spin-based memories, and to simultaneously offer a palette of new functionalities. Analysis of the memory aspect indicates that the SOTFET can offer orders of magnitude increase in the on-off resistance ratio compared to existing magnetic memories, which can potentially lower the operation energy significantly. We establish a quantitative model of the operations of the SOTFET. From the model, the materials needs for the successful operation are identified and the feasibility of the SOTFET is proved in a properly designed CoFe/BiFeO₃ gate stack.