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

Y2O3 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 H2O process. The exponential attenuation of Ga 3d photoelectrons confirmed the laminar growth of ALD-Y2O3. 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 H2O 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 Y2O3 films on the GaAs substrate. The resulting coordinatively unsaturated Y–O pairs of Y2O3 open the next ALD series. The absence of Ga2O3, As2O3, and As2O5 states may play an important role in the attainment of low interfacial trap densities (D it) of