Chemical bonding states and energy band gap of SiO2-incorporated La2O3 films on n-GaAs (001)

La-silicate of (La2O3)0DDT6(SiO2)0DDT4 was prepared by e-beam evaporation of mixed oxides target to control the chemical bonding state and band structure of La2O3 film on n-GaAs (001). Prior to deposition of La-silicate film, sulfur passivation was performed on the surface of GaAs. The composition and uniformity of La-silicate film were simulated from the ratio of photoelectron intensity, ILa 4d/ISi 2p, using angle resolved X-ray photoelectron spectroscopy. The formation of hydroxide phase was effectively prohibited when La-silicate is formed. Energy band gap of La2O3 and La-silicate were estimated as ~5DDT6 eV and ~6DDT5 eV, respectively, by combining valence band and absorption spectra. The change in the energy band structure with regard to n-GaAs was correlated with electrical properties. An enhanced conduction band offset of La-silicate is evidenced by Fowler-Nordheim tunneling mechanism.