Structural analysis, elemental profiling, and electrical characterization of HfO₂ thin films deposited on In_0.53Ga_0.47As surfaces by atomic layer deposition

In this work results are presented on the structural analysis, chemical composition, and interface state densities of HfO₂ thin films deposited by atomic layer deposition (ALD) from Hf[N(CH₃)₂]₄ and H₂O on In_0.53Ga_0.47As/InP substrates. The structural and chemical properties are investigated using high resolution cross-sectional transmission electron microscopy and electron energy loss spectroscopy. HfO₂ films (3–15 nm) deposited on In_0.53Ga_0.47As are studied following a range of surface treatments including in situ treatment of the In_0.53Ga_0.47As surface by H₂S exposure at 50–350 °C immediately following the metal organic vapor phase epitaxy growth of the In_0.53Ga_0.47As layer, ex situ treatment with (NH₄)₂S, and deposition on the native oxides of In_0.53Ga_0.47As with no surface treatment. The structural analysis indicates that the In_0.53Ga_0.47As surface preparation prior to HfO₂ film deposition influences the thickness of the HfO₂ film and the interlayer oxide. The complete interfacial self-cleaning of the In_0.53Gas_0.47As native oxides is not observed using an ALD process based on the Hf[N(CH₃)₂]₄ precursor and H₂O. Elemental profiling of the HfO₂/In_0.53Ga_0.47As interface region by electron energy loss spectroscopy reveals an interface oxide layer of 1–2 nm in thickness, which consists primarily of Ga oxides. Using a conductance method approximation, peak interface state densities in the range from 6×10¹² to 2×10¹³ cm^-2 eV^-1 are estimated depending on the surface preparation.