Band offset control of Gd 2O 3/ n-GaAs (001) structure by incorporation of SiO 2

Abstract

The band gap and band offset of Gd 2O 3 gate oxide film on n-GaAs (001) could be controlled by the incorporation of SiO 2. Prior to the deposition of the gate oxide, the GaAs surface was passivated with sulfur. From the observation of 3 p 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 4 d was observed when SiO 2 was incorporated into Gd 2O 3 and this could be explained by the different electronegativity of second nearest neighbor element, in this work, Si. Energy band gaps of Gd 2O 3 and (Gd 2O 3) 0.5(SiO 2) 0.5 were measured as ∼5.4 and ∼6.8 eV, respectively, using energy loss spectra of O 1 s photoelectron lines. The change in the energy band structure of Gd 2O 3 with regard to n-GaAs due to the incorporation of SiO 2 was demonstrated by correlating band gap values and valence-band maximum energy. An enhanced conduction-band offset of (Gd 2O 3) 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.