Abstract
The importance of using a low-transmission tunnel barrier for electrical spin injection from a ferromagnetic metal to a semiconductor is experimentally tested. A set of ferromagnet–insulator–two-dimensional electron-gas device stuctures is fabricated. Spin-dependent transport is measured in both diode and potentiometric geometries. Results are compared for devices with junction resistances that vary by an order of magnitude. The spin polarization of the junction current is about 40% for high-resistance barriers, with little temperature dependence over the range 4 K< T<295 K.