Electrical spin injection and accumulation in CoFe/MgO/Ge contacts at room temperature

We report the all-electrical spin injection and detection in CoFe/MgO/moderately doped n-Ge contact at room temperature (RT), employing three-terminal Hanle measurements. A sizable spin signal of {~}170 k{Ω} {μ}m² has been observed at RT, and the analysis using a single-step tunneling model gives a spin lifetime of {~}120 ps and a spin diffusion length of {~}683 nm in Ge. The observed spin signal shows asymmetric bias and temperature dependences which are strongly related to the asymmetry of the tunneling process.