  Surface passivation with acidic (NH4)2S solution is shown to be effective in
improving the interfacial and electrical properties of HfO2/GaSb metal oxide
semiconductor devices. Compared with control samples, those treated with acidic
(NH4)2S solution showed great improvements in frequency dispersion, gate
leakage current and interface trap density. These improvements were attributed
to the acidic (NH4)2S solution enhancing passivation of the substrates, which
was analyzed from the perspective of chemical mechanism and confirmed by X-ray
photoelectron spectroscopy and high-resolution cross-sectional transmission
electron microscopy.
