Structural analysis, elemental profiling, and electrical characterization of HfO₂ thin films deposited on In0.53 Ga0.47 As 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 H₂ O on In_0.53 Ga _0.47 As/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_0.53 Ga_0.47 As are studied following a range of surface treatments including in situ treatment of the In_0.53 Ga_0.47 As surface by H₂ S exposure at 50-350 °C immediately following the metal organic vapor phase epitaxy growth of the In_0.53 Ga_0.47 As layer, ex situ treatment with (NH ₄)₂ S, and deposition on the native oxides of In _0.53 Ga_0.47 As with no surface treatment. The structural analysis indicates that the In_0.53 Ga_0.47 As 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_0.53 Gas_0.47 As native oxides is not observed using an ALD process based on the Hf [N (CH₃) ₂] ₄ precursor and H₂ O. Elemental profiling of the HfO₂ / In_0.53 Ga_0.47 As 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× 10 ¹² to 2× 10¹³ cm^-2 eV^-1 are estimated depending on the surface preparation.