Increase in spin injection efficiency of a CoFe/MgO(100) tunnel spin injector with thermal annealing

Postgrowth thermal annealing of a CoFe/MgO(100) tunnel spin injector grown on aGaAs/AlGaAs quantum well structure results in a significantly increased spin injection efficiency as inferred from the polarization of heavy-hole electroluminescence from a quantum well optical detector. The as-deposited sample displayed an initial polarization at 100 K of 43%, which was increased to 52% after a 1 h anneal at 300 deg. C, and finally to 55% after a second 1 h anneal at 340 deg. C. The polarization remained unchanged upon further annealing to temperatures as high as 400 deg. C. These results show that tunnel spin injectors based on CoFe/MgO are robust with high thermal stability, making them useful for device applications