Internal photoemission of electrons and holes from (100)Si into HfO2

Abstract
The electron energy band alignment at the Si/HfO 2 interfaces with different interlayers ( Si 3 N 4 , SiON, and SiO 2 ) is directly determined using internal photoemission of electrons and holes from Si into the Hf oxide. Irrespective of the interlayer type, the energy barrier for the Si valence electrons was found to be equal 3.1±0.1 eV , yielding the conduction band offset of 2.0±0.1 eV . Photoemission of holes is effectively suppressed by SiON and SiO 2 interlayers, yet it is observed to occur across the Si 3 N 4 interlayer with a barrier of 3.6±0.1 eV , which corresponds to a Si/HfO 2 valence band offset of 2.5±0.1 eV . The HfO 2 band gap width of 5.6 eV, thus derived from the band offsets, coincides with the bulk value obtained from the oxide photoconductivity spectra.