Cobalt-Al2O3-silicon tunnel contacts for electrical spin injection into silicon

The resistance of Co-Al2O3-Si tunnel contacts for electrical spin injection from a ferromagnet into silicon is investigated. The contacts form a substantial Schottky barrier, 0.7 eV, which plays a dominant role in the electronic transport. On Si with a low doping concentration (similar to 10(15) cm(-3)), the contact resistance is affected by the Al2O3 tunnel barrier only in the forward bias. In the reverse bias (the spin injection condition), the Schottky barrier results in a very high contact resistance, similar to 10(2) Omega m(2). While the contact resistance is improved to similar to 10(-2) Omega m(2) using Si with a high doping concentration (similar to 5x10(19) cm(-3)), it is still about five to six orders of magnitude higher than the value needed for resistance matching to silicon. (C) 2006 American Institute of Physics.