Comparison of Fe/Schottky and Fe/Al_(2)O_(3) tunnel barrier contacts for electrical spin injection into GaAs

摘要

We compare electrical spin injection from Fe films into identical GaAs-based light-emitting diodes (LEDs) using different tunnel barriers—a reverse-biased Fe/AlGaAs Schottky contact and an Fe/Al_(2)O_(3) barrier. Both types of structures are formed in situ using a multichamber molecular-beam epitaxy system. A detailed analysis of the transport data confirms that tunneling occurs in each case. We find that the spin polarization achieved in the GaAs using the Al_(2)O_(3) barrier is 40% (best case; 30% typical), but the electrical efficiency is significantly lower than that of the Fe Schottky contact.