Electron spin transport and communication with nuclear spin in vertical metal-SiGe-metal bonding samples – ENSEMBLE

Spin-polarized electron transport in semiconductors has been proposed as the basis for an entirely new class of electronic devices. Exploiting the electron spin in semiconductors for this purpose is appealing thanks to: 1) three orders of magnitude longer of spin-coherence time than metal systems; 2) possibility of integrating logic operations, communications and storage within the same materials technology; 3) coherent spin-enabled device operating at the precession frequency of electron spins (from GHz to THz); 4) spin accumulation over long distances and the associated pure spin currents generation. As a core material of semiconductor electronic device, silicon also shows its excellent characteristic in spintronics. The weak spin–orbit coupling in Si results in a very long spin lifetime (µs timescale at 60K), which is several orders of magnitude larger than other semiconductors like GaAs. By using Si to transport spin over long distance and using SiGe to control spin orientation with electric field, a variety of novel functionalities can be designed for future Si-based spintronics devices. In addition, as the n-type dopant 31P in Si has a nuclear spin s=1/2 with 100% in isotropy and 95% of Si is 28Si which has zero nuclear spin, this provide an ideal material background to study the hyperfine interaction of nuclear spin and electron spin in order to use 31P nuclear spin as a solid-state quantum memory for quantum computation.
The aim of this project is to take advantage of our recent developed ultra-high vacuum (UHV) wafer bonding technology to fabricate vertical structure with alternating ferromagnetic metal (FM) and SiGe semiconductor (SC) materials. The ability to fabricate such structures, mostly impossible with classical growth techniques like MBE, will give us the opportunity to 1) study the spin-transport properties in Si, Ge, SixGe1-x alloy and SiGe nanostructures (QWs and QDs) in two different regimes: non-equilibrium and equilibrium; 2) explore the possibility to use highly spin-polarized electron to interact and communicate with nuclear spin via electron-nuclear spin hyperfine interaction; 3) discover new mangetoresistance effect combining with the quantum well states and coulomb blockade inside Si tunnel barrier; 4) generate multi-states spin photocurrent by using light as an addition control tool. This project could have a significant impact to the actual information and communication technology.