ZrO2 gate dielectric films were fabricated on n-GaAs substrates by atomic layer deposition (ALD), using metal organic chemical vapor deposition (MOCVD)-derived ultrathin Gd2O3 film as interfacial control layer between ZrO2 and n-GaAs. The interfacial structure, capacitance-voltage and current-voltage properties of ZrO2/n-GaAs and ZrO2/Gd2O3/n-GaAs metal-oxide-semiconductor (MOS) capacitors have been investigated. The introduction of an ultrathin Gd2O3 control layer can effectively suppress the formation of As oxides and high valence Ga oxide at the high k/GaAs interface which evidently improved the electrical properties of GaAs-based MOS capacitors, such as higher accumulation capacitance and lower leakage current density. It was found that the current conduction mechanism of MOS capacitors varied from Poole-Frenkel emission to Schottky-Richardson emission after introducing the thin Gd2O3 layer. The band alignments of interfaces for ZrO2/GaAs and ZrO2/Gd2O3/GaAs were established, which indicates that the conduction band offset (CBO) for ZrO2/GaAs and ZrO2/Gd2O3/GaAs stacks are similar to 1.45 and similar to 1.62 eV, correspondingly. (C) 2013 Elsevier B. V. All rights reserved.