Atomic Nature of the Growth Mechanism of Atomic Layer Deposited High-κ Y2O3 on GaAs(001)-4 × 6 Based on in Situ Synchrotron Radiation Photoelectron Spectroscopy

Y 2 O 3 was in situ deposited on a freshly grown molecular beam epitaxy GaAs(001)-4 × 6 surface by atomic layer deposition (ALD). In situ synchrotron radiation photoemission was used to study the mechanism of the tris(ethylcyclopentadienyl)yttrium [Y(CpEt) 3 ] and H 2 O process. The exponential attenuation of Ga 3d photoelectrons confirmed the laminar growth of ALD-Y 2 O 3 . In the embryo stage of the first ALD half-cycle with only Y(CpEt) 3 , the precursors reside on the faulted As atoms and undergo a charge transfer to the bonded As atoms. The subsequent ALD half-cycle of H 2 O molecules removes the bonded As atoms, and the oxygen atoms bond with the underneath Ga atoms. The product of a line of Ga-O-Y bonds stabilizes the Y 2 O 3 films on the GaAs substrate. The resulting coordinatively unsaturated Y-O pairs of Y 2 O 3 open the next ALD series. The absence of Ga 2 O 3 , As 2 O 3 , and As 2 O 5 states may play an important role in the attainment of low interfacial trap densities ( D it ) of <10 12 cm -2 eV -1 in our established reports.