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) Al2O3 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.

Graphical abstractThis work presents the realization of the chemical bonding configurations at in-situ ALD-Al2O3/pristine MBE grown Ga-rich n-GaAs (100)-4×6 interface without the native oxides and chemical surface treatments. Our results are conducive to the recognition of the bonding, which may cause pronounced frequency dispersion in C-V curves.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► ALD-Al2O3 was in-situ deposited on pristine MBE grown GaAs(001)-4×6. ► In-situ RHEED, STM and synchrotron-radiation photoemission were utilized in this study. ► The first cycle of ALD-Al2O3 process reacted immediately with the GaAs surface. ► AsOx and the As(1+) were suggested to form at the interface induced by ALD-Al2O3 process.