Characterization of aluminum oxyfluoride barrier in magnetic tunnel junctions

The electrical characteristics and the interface structure of magnetic tunnel junctions with aluminum oxyfluoride barrier were studied. Compared to conventional junctions with aluminum oxide tunnel barrier, junctions with aluminum oxyfluoride barrier exhibit larger and nearly constant tunneling magnetoresistance (TMR) values over a wide range of junction resistance and show a smaller bias dependence of TMR, a smaller temperature dependence of junction resistance, and higher effective barrier height. The cross sectional TEM image demonstrates that the junction with oxyfluoride barrier has excellent barrier flatness and smooth interfaces. X-ray photoelectron spectroscopy indicates that the fluorine forms an aluminum oxyfluoride barrier together with oxygen and that the growth of fluorine-rich oxyfluoride layer near the top surface of the barrier plays an important role in the formation of the highly insulating barrier, resulting in nearly ideal barrier/electrode interfaces without a detrimental magnetically dead layer. (C) 2004 American Institute of Physics.