Energy barriers between (100)Si and Al 2O 3 and ZrO 2-based dielectric stacks: internal electron photoemission measurements

Abstract

Electron energy barriers between the valence band of (100)Si and the conduction bands of ultrathin Al 2O 3 and ZrO 2 insulators grown by atomic-layer deposition were determined using internal photoemission of electrons. The barriers for Al 2O 3 and ZrO 2 are found to be 3.25±0.08 and 3.1±0.1 eV, respectively, i.e. significantly lower than for SiO 2 (4.25±0.05 eV). Thermal oxidation at 650–800°C strongly suppresses tunneling current through enhancement of the barriers at the Si/Al 2O 3 and Si/ZrO 2 interfaces. However, it does not reduce the high density of band tail states in the insulators suggesting that silicates are formed.