Annealing reduces leakage current in MBE grown AlScN and AlYN films

Ternary aluminum scandium nitride (AlScN) and aluminum yttrium nitride (AlYN) are emerging wide-bandgap piezoelectric and ferroelectric materials with significant potential for next-generation electronic devices. This work investigates the impact of post-growth annealing on the structural, electrical, and piezoelectric properties of AlScN and AlYN thin films grown by plasma-assisted by molecular beam epitaxy on tungsten electrodes. Annealing is performed in vacuum, air, and nitrogen atmospheres at temperatures ranging from 750 to 1100 °C. It is observed that annealing in air and nitrogen lowers the leakage current in AlScN and AlYN films. Piezoelectric coefficient (d33) enhancements as high as 137 pm/V for AlScN and 8.05 pm/V for AlYN are observed for less leaky, nitrogen-annealed samples at 750 °C. Preservation of ferroelectric switching properties post-annealing is confirmed by piezo-response force microscopy and PUND measurements. These findings highlight the role of thermal treatments on the performance of AlScN and AlYN for piezoelectric, ferroelectric, and high-K dielectric device applications.