HfO 2 gate dielectric on ( NH 4 ) 2 S passivated ( 100 ) GaAs grown by atomic layer deposition

The interface between hafnium oxide grown by atomic layer deposition and (100) GaAs treated with HCl cleaning and (NH4)2S 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-bylayer removal of the hafnia film revealed a small amount of As2O3 formed at the interface during the dielectric deposition. Traces of arsenic and sulfur out-diffusion into the hafnia film were observed after a 450 o C post-deposition anneal, and may be the origins for the electrically active defects. Transmission electron microscopy cross section images showed thicker HfO2 films for a given precursor exposure on S-treated GaAs versus the SLAC-PUB-12802 September 2007 Submitted to Journal of Applied Physics 2 non-treated sample. In addition, the valence-band and the conduction-band offsets at the HfO2/GaAs interface were deduced to be 3.18 eV and a range of 0.87-0.97 eV, respectively. It appears that HCl+(NH4)2S treatments provide a superior chemical passivation for GaAs and initial surface for ALD deposition.