Spin-Based Devices for Digital Applications

Scaling of semiconductor devices is the main driving force behind an outstanding performance increase of modern integrated circuits. However, it is apparent that transistor scaling shows signs of saturation, and an introduction of new solutions for energy-efficient computation becomes paramount. The electron spin offers additional functionality to digital switches based on field-effect transistors. SpinFETs and SpinMOSFETs are promising devices, with nonvolatility introduced through the relative magnetization orientation between the ferromagnetic source and drain. Although several fundamental problems including spin injection from metal ferromagnets to a semiconductor, spin propagation and relaxation, as well as spin manipulation by the gate voltage were successfully demonstrated, increasing the magnetoresistance ratio as well as achieving efficient spin control represent the challenges to be resolved. Magnetic tunnel junctions are perfectly suited as key elements of nonvolatile CMOS-compatible magnetoresistive memory. Purely electrically addressable spin-transfer torque and spin-orbit torque magnetoresistive memories are superior compared to flash memories and will compete with DRAM and SRAM. MRAM possesses a simple structure, long retention time, high endurance, and fast operation speed. In addition, a combination of nonvolatile elements with CMOS devices allows to bring close or to even shift data processing capabilities into the nonvolatile segment. This paves the way for a new low-power and high-performance computing paradigm based on logic-in-memory and in-memory computing architectures, where the same nonvolatile elements are used to store and to process the information.