The properties of high-k dielectric layers of materials such as HfO₂ on III-V surfaces are interest for the development of III-V MOSFETs since such devices will require high-k/metal gate stacks designed to minimize gate leakage. In a study of potentially high-mobility InGaAs-based structures, we have focused on the growth of HfO₂ overlayers on high indium content (53% In) lattice-matched In_0.53Ga_0.47As layers grown by MOVPE on InP substrates. In an attempt to address the problems associated with native oxides we have explored the use of both a wet chemical ex-situ pre-growth treatment and a novel in-situ surface treatment performed at the end of the InGaAs MOVPE growth cycle. The former ex-situ treatment involves the use of aqueous (NH₄)₂S solution while the latter in-situ treatment involves introducing H₂S to the environment of the MOVPE growth reactor following completion of the growth itself.

XPS analysis reveals that as compared to an untreated surface, both passivation approaches significantly inhibit the formation of native oxides on the InGaAs surface upon exposure to ambient conditions. The electrical characteristics of gate stacks prepared after ALD growth of HfO₂ from tetrakis dimethylamido hafnium (Hf(NCH₃)₂)₄) and water were evaluated using Pd/HfO₂/In_0.53Ga_0.47As/InP MOS structures. While both passivation methods yielded good results, the use of the in-situ H₂S passivation of the InGaAs at 50^oC prior to HfO₂ deposition was found to be particularly effective in terms of the maximum accumulation capacitance, dielectric leakage and interface state densities. These results were achieved without post deposition annealing of the overall Pd/HfO₂/In_0.53Ga_0.47As/InP MOS structure. The results indicate that the interfacial Fermi-level is unpinned for both in-situ and ex-situ passivation approaches. We discuss these results in terms of possible models for the passivated interface and the subsequent mechanisms for the initial growth of the HfO₂ layer.

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