Magnetic tunnel junctions with AlN and AlNxOy barriers

Nonoxide tunnel barriers such as AlN are of interest for magnetic tunnel ju nctions to avoid the oxidation of the magnetic electrodes. We have investig ated the fabrication and properties of thin AlN-based barriers for use in l ow resistance magnetic tunnel junctions. Electronic, magnetic and structura l data of tunnel valves of the form Ta (100 Angstrom)/PtMn (300 Angstrom)/C oFe20 (20 Angstrom -25 Angstrom)/barrier/CoFe20 (10-20 Angstrom)/NiFe16 (35 -40 Angstrom)/Ta (100 Angstrom) are presented, where the barrier consists o f AlN, AlNxOy or AlN/AlOx with total thicknesses between 8 and 15 Angstrom. The tunnel junctions were sputter deposited and then lithographically patt erned down to 2 x 2 mum(2) devices. AlN was deposited by reactive sputterin g from an Al target with 20%-35% N-2 in the Ar sputter gas at room temperat ure, resulting in stoichiometric growth of AlNx (x = 0.50 +/-0.05), as dete rmined by RBS. TEM analysis shows that the as-deposited AlN barrier is crys talline. For AlN barriers and AlN followed by natural O-2 oxidation, we obt ain tunnel magnetoresistance > 10% with specific junction resistance R-j do wn to 60 Ohm mum(2). (C) 2001 American Institute of Physics.