Electrical spin injection into a normal modulation-doped AlGaAs/GaAs heterostructure with a CoFe spin source

We demonstrated electrical spin injection from a CoFe spin source into a two-dimensional electron gas (2DEG) channel formed in an AlGaAs/GaAs-based normal modulation-doped structure through the observation of spin-valve signals at 5 K. Although a 15-nm-thick AlGaAs layer with a Si δ-doping existed between the CoFe and 2DEG channels, the spin polarization of the injector and detector electrodes was slightly larger than that in the structure without the AlGaAs layer. We experimentally found that the magnitude of spin-valve signals was strongly dependent on the detector bias current Id in both the 2DEG channel and bulk n-GaAs channel, whose dominant factor is the modulation of the spin diffusion length with Id through drift transport in the case of the 2DEG channel and the modulation of the spin polarization at the detector/GaAs interface with Id through the biasing of the detector junction in the case of the bulk n-GaAs channel. These findings will provide valuable insights for developing future 2DEG-based spintronic devices.