In situ atomic layer deposition and synchrotron-radiation photoemission study of Al₂O₃ on pristine n-GaAs(0 0 1)-4 × 6 surface

This work presents the in situ reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and synchrotron-radiation photoemission studies for the morphological and interfacial chemical characterization of in situ atomic layer deposited (ALD) Al₂O ₃ on pristine molecular beam epitaxy (MBE) grown Ga-rich n-GaAs (1 0 0)-4 × 6 surface. Both the RHEED pattern and STM image demonstrated that the first cycle of ALD-Al₂O₃ process reacted immediately with the GaAs surface. As revealed by in situ synchrotron-radiation photoemission studies, two types of surface As atoms that have excess in charge in the clean surface served as reaction sites with TMA. Two oxidized states were then induced in the As 3d core-level spectra with chemical shifts of +660 meV and +1.03 eV, respectively.