Characterization of Y_2O_3 gate dielectric on n-GaAs substrates

摘要

Physical and electrical properties of sputtered deposited Y_2O_3 films on NH_4OH 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_2O_3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 10~(12)V~(-1) cm~(-2)). The results show that the deposition of Y_2O_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_2O_3-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_2O_3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y_2O_3-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.