Fabrication and interface electrical properties of Fe₃O₄/MgO/GaAs(100) spin contacts

Moderately doped n-GaAs(100) substrates (n= 5 x 10 17cm3 ) with In Ohmic back contacts were annealed in the growth chamber with a base pressure of 1 x 10-8 mbar for 60 min at 830 K prior to the film stack growth. MgO layer was then grown by e-beam evaporation at a rate of 2 Amin-1 while the substrates were kept at 673 K, followed by postgrowth annealing of a 3.0 nm thick epitaxial Fe at 500 K in an O2 partial pressure of 5 x 10-5 mbar for 10 min. As for Fe3O4-GaAs(100), the tunneling barrier deposition was skipped. The epitaxial spin contacts were ex situ characterized by current-voltage (I-V) measurements. The junction size ranges from 25 to 200 μm square and were patterned by standard photolithography and wet etching using a 50 nm thick thermally evaporated Au layer as an etch mask.