Band offset control of Gd₂O₃/n-GaAs (001) structure by incorporation of SiO₂

The band gap and band offset of Gd₂O₃ gate oxide film on n-GaAs (001) could be controlled by the incorporation of SiO₂. Prior to the deposition of the gate oxide, the GaAs surface was passivated with sulfur. From the observation of 3p photoelectron lines of Ga and As, S-passivated GaAs surface was found to be not-oxidized during the formation of the gate oxide films. The photoelectron binding energy shift of Gd 4d was observed when SiO₂ was incorporated into Gd₂O₃ and this could be explained by the different electronegativity of second nearest neighbor element, in this work, Si. Energy band gaps of Gd₂O ₃ and (Gd₂O₃)_0.5(SiO ₂)_0.5 were measured as ∼5.4 and ∼6.8 eV, respectively, using energy loss spectra of O 1s photoelectron lines. The change in the energy band structure of Gd₂O₃ with regard to n-GaAs due to the incorporation of SiO₂ was demonstrated by correlating band gap values and valence-band maximum energy. An enhanced conduction-band offset of (Gd₂O₃)_0.5(SiO ₂)_0.5 resulted in the decrease of leakage current density. Fowler-Nordheim tunneling mechanism was applied to explain the increase of barrier height.