Ferroelectricity in boron-substituted aluminum nitride thin films

This manuscript demonstrates ferroelectricity in B-substituted AlN thin films and a complementary set of first-principles calculations to understand their structure-property relationships. Al₁--ₗBₗN films are grown by dual-cathode reactive magnetron sputtering on (110) W/ (001) Al₂O₃ substrates at 300^ at compositions spanning x=0 to x=0. 20. X-ray diffraction studies indicate a decrease in both the c and a lattice parameters with increasing B concentration, resulting in a decrease in unit cell volume and a constant c/a axial ratio of 1. 60 over this composition range. Films with 0. 020. 15 display ferroelectric switching with remanent polarizations exceeding 1250. 16em{0ex}0. 16em{0ex}cm^--2 while maintaining band gap energies of >5. 20. 16em{0ex}eV. The large band gap allows low frequency hysteresis measurement (200 Hz) with modest leakage contributions. At B concentrations of x>0. 15, c-axis orientation deteriorates and ferroelectric behavior is degraded. Density-functional theory calculations corroborate the structural observations and provide predictions for the wurtzite u parameter, polarization reversal magnitudes, and composition-dependent coercive fields.