MgGa2O4 as alternative barrier for perpendicular MRAM junctions and VCMA

Abstract

The CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) is the central element of any high performance perpendicular Magnetoresistive Random Access Memory (MRAM) device. The MgO tunnel barrier, in contact with CoFeB films at both sides in the magnetic tunnel junction, provides a high tunnel magneto resistance (TMR) and perpendicular magnetic anisotropy (PMA) thanks to the high crystalline quality of the MgO/CoFeB interface achieved upon post-deposition annealing. We study MgGa2O4 as an alternative barrier material due to its lower bandgap and show how to introduce it into state-of-the-art perpendicular MRAM stacks. We demonstrate that thin MgO films at both sides of the barrier are key to ensure a proper crystallization and induce reference layer and free layer perpendicular magnetic anisotropy. Consequently, a stack incorporating a MgGaxOy barrier with full PMA and TMR > 100% can be fabricated with a resistance-area (RA) product as low as 50 omega mu m(2), which is of strong interest as a potential barrier in the field of voltage control magnetic anisotropy MRAM.