Spin injection through energy-band symmetry matching with high spin polarization in atomically controlled ferromagnet/ferromagnet/semiconductor structures

Electrical injection of spin-polarized electrons from ferromagnets into semiconductors has been generally demonstrated through a tunneling process with insulator barrier layers that can dominate the device performance, including the electric power at the electrodes. Here, we show an efficient spin injection technique for a semiconductor using an atomically controlled ferromagnet/ferromagnet/semiconductor heterostructure with low-resistive Schottky-tunnel barriers. On the basis of symmetry matching of the electronic bands between the top highly spin-polarized ferromagnet and the semiconductor, the magnitude of the spin signals in lateral spin-valve devices can be enhanced by up to one order of magnitude compared to those obtained with conventional ferromagnet/semiconductor structures. This approach provides a new solution for the simultaneous achievement of highly efficient spin injection and low electric power at the electrodes in semiconductor devices, leading to novel semiconductor spintronic architectures at room temperature. Atomically precise deposition techniques can reduce the power demands of devices that use electron spins for high-speed and low-power computing. Spintronic systems often rely on quantum mechanical tunneling to move electrons with specific spins from magnets to semiconductors, but this process requires significant electrical energy. Kohei Hamaya from Osaka University in Toyonaka, Japan, and colleagues now report that these tunneling barriers can be tweaked by growing iron films only a few atomic layers thick between magnets and semiconductors. The team’s studies revealed that the ultrathin films modified the energy levels in the interface region, creating an easy-to-access tunneling route for spin-polarized current. Because the iron atoms removed the need for insulating materials typically used in tunnel junctions, the device could operate at power levels an order of magnitude lower than usual. We show an efficient spin injection technique for a semiconductor using an atomically controlled ferromagnet/ferromagnet/semiconductor heterostructure with low-resistive Schottky-tunnel barriers. Even for semiconductor spintronic devices, the symmetry matching of electronic bands between the ferromagnet and the semiconductor should be considered. This approach provides a new solution for the simultaneous achievement of highly efficient spin injection and low electric power at the electrodes in semiconductor devices at room temperature.