The interface between hafnium oxide grown by atomic layer deposition and (100) GaAs treated with HCl cleaning and (NH 4 ) 2 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-bylayer removal of the hafnia film revealed a small amount of As 2 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 o C post-deposition anneal, and may be the origins for the electrically active defects. Transmission electron microscopy cross section images showed thicker HfO 2 films for a given precursor exposure on S-treated GaAs versus the SLAC-PUB-12802 September 2007Submitted to Journal of Applied Physics 2 non-treated sample. In addition, the valence-band and the conduction-band offsets at the HfO 2 /GaAs interface were deduced to be 3.18 eV and a range of 0.87-0.97 eV, respectively. It appears that HCl+(NH 4 ) 2 S treatments provide a superior chemical passivation for GaAs and initial surface for ALD deposition.

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