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We analyze the field and temperature dependence of electron currents through atomic-layer-deposited thin (3.6–6 nm) sheets of Al2O3 which were annealed above the crystallization temperature. On the basis of electrical characterization and numerical simulation that includes trap-assisted transport as well as the band bending in the contact regions, we have identified three characteristic field regions in which the currents are dominated by elastic trap-assisted tunneling, Frenkel–Poole hopping, or Fowler–Nordheim tunneling. We find that the Frenkel–Poole traps lie in a narrow band about 1.2 eV below the conduction band minimum of Al2O3, whereas the energetic distribution of the elastic traps is broad and has a tail that reaches far into the band gap. The numerical results are compatible with a Si/Al2O3 conduction band offset of 2.7 eV.

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