Electronic structure and energy band offsets for ultrathin silicon nitride on Si(1 0 0)

For the interfaces of CVD Si3N4 on Si(1 0 0) and directly-nitrided Si(1 0 0), chemical bonding features, energy band offsets and defect state density distributions have been studied using high-resolution X-ray photoelectron spectroscopy and total photoelectron yield spectroscopy. At nitride–Si(1 0 0) interfaces, SiN bonding states in which each Si atom is bonded with one or three N atoms are formed predominantly, being presumably related to the structural strain induced by SiN bonding at the interface. For nearly stoichiometric SiNx (x≥1.3) in the thickness range of 1.0–17 nm which was prepared by 750 °C CVD or 700 °C direct-nitridation, the energy band gap was determined to be 5.4±0.1 eV from the energy loss spectra of N 1s photoelectrons. By analyzing the valence band spectra of thin SiNx/Si(1 0 0) heterostructures, the valence band offset between such SiNx and Si(1 0 0) was obtained to be 1.9±0.1 eV. For the direct-nitridation of Si(1 0 0) at 600 or 700 °C, an interface state density as low as ∼1010 eV−1 cm−2 near Si midgap was confirmed by total photoelectron yield measurements.