Electrical spin injection from ferromagnet into an InAs quantum well through a MgO tunnel barrier

The electrical spin injection from Ni81Fe19 (NiFe) into an InAs quantum well through a MgO tunneling barrier has been investigated for potential application to an InAs-based spin field-effect transistor. The insertion of a 2-nm-thick MgO tunnel barrier between NiFe and InAs increased the junction resistance by two orders of magnitude compared with that without a MgO barrier. The sample with a MgO barrier showed a clear nonlocal spin-valve signal at 1.4 K, possibly due to the alleviation of the impedance mismatching problem. The estimated spin polarization was 8.1%, which is higher than any reported in the literature for a NiFe/InGaAs Schottky junction. (C) 2014 The Japan Society of Applied Physics