Characterization of Y2O3 gate dielectric on n-GaAs substrates
Abstract Physical and electrical properties of sputtered deposited Y 2 O 3 films on NH 4 OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y 2 O 3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion ( 12  eV −1  cm −2 ). The results show that the deposition of Y 2 O 3 on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high- k /GaAs interface. The Al/Y 2 O 3 /n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10 −6  A cm −2 at a V FB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole–Frenkel emission takes over at high electric fields. The energy band alignment of Y 2 O 3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y 2 O 3 /n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.