Interface-controlled Gd ₂ O ₃ /GaAs system for ferroelectric memory application

The formation of Gd ₂ O ₃ /substrate-GaAs structure was accomplished by two-step electron-beam (e-beam) deposition including ultra-thin Gd-metal and successive Gd ₂ O ₃ layers. The deposition was carried out on HCl-cleaned GaAs containing elemental As on it. The pre-deposition of Gd-metal removes elemental As state in GaAs surface and forms interfacial state free from GaAs-oxides. However, Gd-metal turns to be oxide during the deposition by absorbing oxygen from GaAs surface and atmosphere. The successive deposition of Gd ₂ O ₃ was performed with in situ anneal of the substrate and this permitted preferential growth of Gd ₂ O ₃ with oriental relationship with substrate GaAs as Gd ₂ O ₃ {1 1 1}〈1 1 0〉||GaAs{0 0 1}〈4 7 0〉 with less than 1.5% of lattice mismatching. Capacitance-voltage (C-V) and current density-voltage (J-V) measurements indicated that the interface was seriously degraded when the anneal temperature exceeded 600 °C. The feasibility of Gd ₂ O ₃ film as a buffer layer for ferroelectric-gate/GaAs structure was proved.