Improved interface properties of an HfO2 gate dielectric GaAs MOS device by using SiNx as an interfacial passivation layer

A GaAs metal-oxide-semiconductor (MOS) capacitor with HfO2 as gate dielectric and silicon nitride (SiNx) as the interlayer (IL) is fabricated. Experimental results show that the sample with the SiNx IL has an improved capacitance-voltage characteristic, lower leakage current density (0.785 x 10(-6) A/cm(2) at V-fb + 1 V) and lower interface-state density (2.9 x 10(12) eV(-1).cm(2)) compared with other samples with N-2- or NH3-plasma pretreatment. The influences of post-deposition annealing temperature on electrical properties are also investigated for the samples with SiNx IL. The sample annealed at 600 degrees C exhibits better electrical properties than that annealed at 500 degrees C, which is attributed to the suppression of native oxides, as confirmed by XPS analyses.