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

Atomic-layer-deposited layers of Al2O3 on (100)Si are shown to transform into γ-Al2O3 when treated at temperatures above 800 °C. The compaction process leads to widening of the alumina band gap and causes an ≈0.5 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 Al2O3 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.