Electrical spin injection in modulation-doped GaAs from an in situ grown Fe/MgO layer

We study spin accumulation in n-doped GaAs that were electrically injected from Fe via MgO using three-terminal Hanle measurement. The Fe/MgO/GaAs structures were prepared in a cluster molecular beam epitaxy that did not require the breaking of the vacuum. We found the crystal orientation relationship of epitaxial structures Fe[100]//MgO[110]//GaAs[110] without evident defects at the interface. Control of depletion width and interface resistance by means of modulation doping improves spin injection, leading to enhanced spin voltage (ΔV) of 6.3-mV at 10-K and 0.8-mV even at 400-K. The extracted spin lifetime and spin diffusion length of GaAs are 220 ps and 0.77-μm, respectively, at 200-K. MgO tunnel barrier grown in situ with modulation doping at the interface appears to be promising for spin injection into GaAs.