Atomically abrupt and unpinned Al2O3/In0.53Ga0.47As interfaces: Experiment and simulation

III-V semiconductor field effect transistors require an insulator/channel interface with a low density of electrically active defects and a minimal interface dipole to avoid Fermi level pinning. We demonstrate that an atomically abrupt and unpinned interface can be formed between an In0.53Ga0.47As (100) channel and an Al2O3 dielectric layer grown by atomic layer deposition (ALD) when oxidation of the substrate surface is prevented before and during oxide deposition. X-ray photoelectron spectra and electron microscopy indicate that in situ desorption of a protective As-2 layer on the In0.53Ga0.47As (100)-4x2 surface followed by ALD of Al2O3 produced an atomically abrupt interface without Fermi level pinning. Temperature-dependent and frequency-dependent capacitance-voltage and conductance-voltage analysis of the resulting Pt/Al2O3/InGaAs capacitors are consistent with movement of the Fermi level through the InGaAs band gap. Moreover, the nearly ideal flat band voltages observed for gate metals of widely varying work function indicate a small oxide/semiconductor interface dipole. Density functional theory calculations of the electronic structure of an ideal amorphous Al2O3/InGaAs (100) interface predict a weak perturbation of the InGaAs electronic structure if its oxidation is avoided, consistent with experiment.