Investigation of interfacial oxidation control using sacrificial metallic Al and La passivation layers on InGaAs
Wallace, Robert M.
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The ability of metallic Al and La interlayers to control the oxidation of InGaAs substrates is examined by monochromatic x-ray photoelectron spectroscopy (XPS) and compared to the interfacial chemistry of atomic layer deposition (ALD) of Al2O3 directly on InGaAs surfaces. Al and La layers were deposited by electron-beam and effusion cell evaporators, respectively, on In0.53Ga0.47As samples with and without native oxides present. It was found that both metals are extremely efficient at scavenging oxygen from III-V native oxides, which are removed below XPS detection limits prior to ALD growth. However, metallic Ga//In/As species are simultaneously observed to form at the semiconductor-metal interface. Upon introduction of the samples to the ALD chamber, these metal bonds are seen to oxidize, leading to Ga/In-O bond growth that cannot be controlled by subsequent trimethyl-aluminum (TMA) exposures. Deposition on an oxide-free InGaAs surface results in both La and Al atoms displacing group III atoms near the surface of the semiconductor. The displaced substrate atoms tend to partially oxidize and leave both metallic and III-V oxide species trapped below the interlayers where they cannot be "cleaned-up" by TMA. For both Al and La layers the level of Ga-O bonding detected at the interface appears larger then that seen following ALD directly on a clean surface.