Band alignments in metal–oxide–silicon structures with atomic-layer deposited Al2O3 and ZrO2

The energy barrier height Φ for electrons at the interfaces of various metals (Mg,Al,Ni,Cu,Au) with nanometer-thin Al2O3 and ZrO2 layers grown on (100)Si by atomic layer deposition has been directly measured using internal photoemission of electrons into the insulator. The behavior of the metal/Al2O3 contacts with increasing metal electronegativity XM resembles that of the metal/SiO2 interfaces with ideality factor dΦ/dXM≈1. The metal/ZrO2 contacts exhibit a less ideal behavior with dΦ/dXM≈0.75. The metal–silicon work function differences in structures with Al2O3 and ZrO2 insulators appear to be considerably larger than in the structures with thermally grown SiO2, suggesting the presence of a negative dipole layer at the metal/deposited oxide interface.