Surface Passivation Using Lanthanide Oxynitrides for GaAs Metal–Oxide–Semiconductor Applications

Abstract

Different lanthanide oxynitrides (LaON, NdON, CeON, and GdON) are applied as the interfacial passivation layers (IPLs) for GaAs metal-oxide-semiconductor (MOS) capacitors with HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as the gate dielectric. The measurement results show that all the IPLs can improve the quality of the HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /GaAs interface by suppressing the in-diffusions of Hf and O toward the GaAs surface from the gate dielectric, and thus the growth of unstable Ga/As oxides as proved by the atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analysis. Among the IPLs, the LaON IPL shows the best passivating effect on the GaAs surface, and so the relevant MOS capacitor exhibits the lowest interface-state density (8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ), smallest flatband voltage (0.65 V), negligible hysteresis (33 mV), lowest gate leakage (1.08 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fb</sub> + 1 V), smallest frequency dispersion (2.85% in accumulation region), and good high-field reliability. NdON exhibits slightly less performance improvement than LaON, but its lower cost and higher moisture resistance can enhance its potential for GaAs surface passivation.