Low resistance and enhanced thermal and electrical stability of the magnetic tunnel junction with a Ti-alloyed Al-oxide barrier

A new Ti-alloyed Al-oxide (TiAlO_x) that has lower resistance than Al₂O₃ is developed as an insulating barrier of magneto tunnel junctions (MTJs) . The microstructure of the barrier and the MTJ is analyzed using transmission electron microscopy, and the rms roughness is characterized by atomic force microscopy. The Ti-alloying effects on the band gap states in Al₂O₃ are studied by X-ray absorption spectroscopy and the theoretical prediction of the band gap changes is experimentally confirmed in transition-metal doped Al₂O₃ systems. It is observed that the junctions with a TiAlO_x barrier have better thermal stability than those with an Al-oxide barrier. Also, the bias voltage and the breakdown voltage of the MTJ are found to increase gradually with Ti concentration. These results show that Ti-alloyed AlO_x is both more structurally and electrically stable than Al₂O₃.