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 2 as the gate dielectric. The measurement results show that all the IPLs can improve the quality of the HfO 2 /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 11 cm -2 eV -1 ), smallest flatband voltage (0.65 V), negligible hysteresis (33 mV), lowest gate leakage (1.08 × 10 -6 A/cm 2 at V fb + 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.