Metal-oxide-semiconductor (MOS) capacitors fabricated by depositing yttrium oxide (Y2O3) using radio frequency sputtering system on top of n-GaAs substrates have been investigated. To study the interface properties, charge trapping behavior and breakdown characteristics of Y2O3 gate dielectric, the MOS capacitors were subjected to constant current stress, high pulse voltage stress and high constant voltage stress. The average value of the cross section of generated traps during electrical stress has been determined from our experimental data. Further the trap charge density, its distribution and location have been investigated by measurements on application and subsequent withdrawal of high pulse voltage stress. Additionally, stress induced leakage current density and time dependent dielectric breakdown characteristics have been obtained and time-to-breakdown exceeding 840 s is observed for Y2O3 gate dielectrics directly deposited on n-GaAs. Our experimental results have been analyzed with simple analytical formulae available in the literature. (C) 2011 Elsevier B.V. All rights reserved.