Modulation of interfacial and electrical properties of HfGdO/GaAs gate stacks by ammonium sulfide passivation and rapid thermal annealing

•Sputtering-derived GaAs/HfGdO gate stack have been deposited.•Surface passivation and rapid thermal annealing lead to the improved electrical properties.•600 °C-annealed HfGdO thin films displays potential application in future CMOS devices.

In this work, the interface chemistry and the reduction of GaAs surface species by using (NH4)2S solution prior to Gd-doped HfO2 (HGO) thin film deposition and the removal of Ga Oxides and elemental As by rapid thermal annealing (RTA) have been investigated by X-ray photoelectron spectroscopy (XPS). Additionally, the effect of the surface passivation and rapid thermal annealing on the electrical properties of MOS capacitors based on sputtering-derived HGO as gate dielectric on GaAs substrate has been detected by means of capacitance-voltage (C-V) and leakage current density-voltage (J-V) measurements. Based on electrical analysis, it can be noted that the constantly improvement of electrical properties, such as the decreases of flat band voltage (Vfb), hysteresis (ΔVfb), oxide charge density (Oox), border trapped oxide charge density (Nbt) and leakage current density, have been observed. Especially, the dielectric constant of 16.72, flat band voltage Vfb of 1.19 V, hysteresis ΔVfb of 0.04 V, leakage current density of 1.54 × 10−5 A/cm2 at bias voltage of 1 V, total positive charge density and border trap charge density of 6.09 × 1012 cm−2 and 2.54 × 1011 cm−2, respectively render 600 °C-annealed HGO thin films, potential high-k gate dielectrics in future CMOS devices.

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