Hf O 2 gate dielectric on (NH4)2S passivated (100) GaAs grown by atomic layer deposition

Abstract

The interface between hafnium oxide grown by atomic layer deposition and (100) GaAs treated with HCl cleaning and ${\left(\mathrm{N}{\mathrm{H}}_4\right)}_2\mathrm{S}$ passivation has been characterized. Synchrotron radiation photoemission core level spectra indicated successful removal of the native oxides and formation of passivating sulfides on the GaAs surface. Layer-by-layer removal of the hafnia film revealed a small amount of ${\mathrm{As}}_2{\mathrm{O}}_3$ formed at the interface during the dielectric deposition. Traces of arsenic and sulfur out diffusion into the hafnia film were observed after a $450°\mathrm{C}$ postdeposition anneal and may be the origins for the electrically active defects. Transmission electron microscopy cross section images showed thicker $\mathrm{Hf}{\mathrm{O}}_2$ films for a given precursor exposure on sulfur treated GaAs versus the nontreated sample. In addition, the valence-band and the conduction-band offsets at the $\mathrm{Hf}{\mathrm{O}}_2∕\mathrm{Ga}\mathrm{As}$ interface were deduced to be $3.18\mathrm{eV}$ and a range of $0.87–1.36\mathrm{eV}$ , respectively. It appears that $\mathrm{H}\mathrm{Cl}+{\left(\mathrm{N}{\mathrm{H}}_4\right)}_2\mathrm{S}$ treatments provide a superior chemical passivation for GaAs and initial surface for atomic layer deposition.