Spin-based MOSFETs for logic and memory applications and spin accumulation signals in CoFe/Tunnel barrier/SOI devices

New innovative ferromagnetic source/drain technologies on Si for next-generation-transistor applications are researched and developed using CoFe/AlO _xn ₊ Si and CoFe/MgO n ₊-Si junctions. As evidence of the spin accumulation in the n ₊-Si conduction channels, nonlocal spin signals and four-terminal nonlocal-Hanle signals are presented for CoFe/MgO/SOI devices. The spin diffusion times determined by four-terminal nonlocal-Hanle signals are consistent with those observed in three-terminal Hanle signals. The relatively long spin diffusion time of τ _s = 1.4 nsec and relatively large spin polarization P =0.43 at room temperature for CoFe/MgO/SOI devices were observed, when fitting to the existing diffusion model for spin injection and accumulation. We have observed the marked enhancement of the absolute value of three-terminal voltage changes via Hanle-type spin precessions (|ΔV|) as a function of interface resistance in the temperature range between 20 K and 300 K.We also have observed the asymmetric bias voltage dependence on ΔV . In terms of the reason of marked enhancement of as a function of interface resistance, the spin absorption into ferromagnet would be most effective. For the explanation of (|ΔV|) the asymmetric bias voltage dependence, we should take into account two additional possible origins.Moreover, we succeed in decreasing the interface resistance for CoFe/MgO/n ₊ -Si junctions down to 36ωμ m ₂ by using evaporation method for MgO deposition.