Synchrotron Radiation Photoemission Study of Ge3N4/Ge Structures Formed by Plasma Nitridation

Abstract

Chemical bonding states and energy band alignment of pure germanium nitride (Ge3N4) layers formed on Ge(100) surfaces by high-density plasma nitridation were characterized by synchrotron radiation photoemission spectroscopy (SR-PES). The core-level shift of 2.31 eV originating from Ge–N bonds (Ge4+) with respect to the bulk Ge 3d5/2 peak position (Ge0+) was determined by peak deconvolution of Ge 3d core-level spectra. In situ SR-PES study on changes in Ge 3d, N 1s, and O 1s core-level spectra during thermal annealing under ultrahigh vacuum (UHV) conditions revealed that oxidized surface layer on Ge3N4 film could be selectively removed at around 500 °C, which was 50 °C lower than the decomposition temperature of Ge3N4. Ge3+ component was found to increase with decreasing Ge4+ component during thermal decomposition of Ge3N4 while no significant change in Ge1+ and Ge2+ components. The Ge3N4 energy bandgap of 3.68 eV was experimentally determined from energy loss spectra of N 1s photoelectrons. The valence band offset at Ge3N4/Ge(100) interfaces were also estimated to be 1.65 eV from valence band spectra, and thus, the energy band alignment between Ge3N4 dielectrics and Ge substrate was determined.