Impact of annealing-induced compaction on electronic properties of atomic-layer-deposited Al2O3

Atomic-layer-deposited layers of ${\mathrm{Al}}_2{\mathrm{O}}_3$ on (100)Si are shown to transform into $\mathrm{\gamma -}{\mathrm{Al}}_2{\mathrm{O}}_3$ when treated at temperatures above $\text{800\hspace{0.05em}°}\mathrm{C}.$ The compaction process leads to widening of the alumina band gap and causes an $\text{≈0.5\hspace{0.17em}}\mathrm{eV}$ upward shift of the oxide conduction band with respect to the Fermi level of Au and Al. In the case of incomplete transformation of the ${\mathrm{Al}}_2{\mathrm{O}}_3$ film, large leakage currents across the oxide are observed, which are explained by the formation of conducting grain boundaries similar to those formed on γ-alumina surfaces.