Impact of ultrathin $Al2O3$ diffusion barriers on defects in high-$k$ $LaLuO3$ on Si

We used depth-resolved cathodoluminescence spectroscopy (DRCLS) to measure trap energies and relative densities in metal/high-$κ$ dielectric $LaLuO3/Si$ stacks, defects produced by $LaLuO3–Si$ interdiffusion, and suppression of these defects by monolayer-thick $Al2O3$ interlayers. DRCLS reveals deep levels at 3.8, 4.2, and 4.7 eV above the valence band, consistent with $LaLuO3$ oxygen vacancies predicted by theory and a 5.5 eV band gap. Oxygen annealing produces $LaLuO3/Si$ interdiffusion that increases 3.8 eV defect density and which a 0.4 nm $Al2O3$ completely removes. Transmission electron microscopy and current leakage results shows that $Al2O3$ prevent $LaLuO3/Si$ silicate layer formation and dramatically lower defects with oxygen annealing.