Impact of Gd_2O_3 passivation layer on interfacial and electrical properties of atomic-layer-deposited ZrO_2 gate dielectric on GaAs

摘要

ZrO_2 gate dielectric films were fabricated on n-GaAs substrates by atomic layer deposition (ALD), using metal organic chemical vapor deposition (MOCVD)-derived ultrathin Gd_2O_3 film as interfacial control layer between ZrO_2 and n-GaAs. The interfacial structure, capacitance-voltage and current-voltage properties of ZrO_2-GaAs and ZrO_2/Gd_2O_3-GaAs metal-oxide-semiconductor (MOS) capacitors have been investigated. The introduction of an ultrathin Gd_2O_3 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 Gd_2O_3 layer. The band alignments of interfaces for ZrO_2/GaAs and ZrO_2/Gd_2O_3/GaAs were established, which indicates that the conduction band offset (CBO) for ZrO_2/GaAs and ZrO_2/Gd_2O_3/GaAs stacks are ～1.45 and ～1.62 eV, correspondingly.