Cascade of Y-shaped spin filters in InAs

For spintronic devices highly spin-polarized currents are required. While the theoretically predicted values for the injection rate of polarized currents in ferromagnet-semiconductor hybrid devices are low, Y-shaped all-semiconductor structures using the Rashba spin-orbit interaction are predicted to provide a high spin polarization at the outputs of these three-terminal devices. The spin-filter effect has been shown by simulations and we present first measurements here. Quantum-point contacts formed by sidegates are employed to decrease the number of conductance channels in the two-dimensional electron system of an InAs channel inserted into an In0.75Al0.25As/In0.75Ga0.25As structures. The devices with channel widths down to 100 nm are prepared by electron-beam lithography and reactive ion-etching to generate. Adding a second filter operating as a detector allows an all-electric measurement of the spin polarization. Cascading more filters will lead to a higher degree of polarization