Structural analysis, elemental profiling, and electrical characterization of HfO2 thin films deposited on In0.53Ga0.47As 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 In0.53Ga0.47As/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 In0.53Ga0.47As are studied following a range of surface treatments including in situ treatment of the In0.53Ga0.47As surface by H2S exposure at 50–350 °C immediately following the metal organic vapor phase epitaxy growth of the In0.53Ga0.47As layer, ex situ treatment with (NH4)2S, and deposition on the native oxides of In0.53Ga0.47As with no surface treatment. The structural analysis indicates that the In0.53Ga0.47As 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 In0.53Gas0.47As 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/In0.53Ga0.47As 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.