title: Preparation of gallium nitride surfaces for atomic layer deposition of aluminum oxide.
abstract: A combined wet and dry cleaning process for GaN(0001) has been investigated with XPS and DFT-MD modeling to determine the molecular-level mechanisms for cleaning and the subsequent nucleation of gate oxide atomic layer deposition (ALD). In situ XPS studies show that for the wet sulfur treatment on GaN(0001), sulfur desorbs at room temperature in vacuum prior to gate oxide deposition. Angle resolved depth profiling XPS post-ALD deposition shows that the a-Al2O3 gate oxide bonds directly to the GaN substrate leaving both the gallium surface atoms and the oxide interfacial atoms with XPS chemical shifts consistent with bulk-like charge. These results are in agreement with DFT calculations that predict the oxide/GaN(0001) interface will have bulk-like charges and a low density of band gap states. This passivation is consistent with the oxide restoring the surface gallium atoms to tetrahedral bonding by eliminating the gallium empty dangling bonds on bulk terminated GaN(0001).
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Kerr
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: E
authors.initials: E
authors.lastname: Chagarov
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: S
authors.initials: S
authors.lastname: Gu
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kaufman-Osborn
authors.affiliation: Department of Nanoscale Science and Engineering, University at Albany-State University of New York, Albany, New York 12222, USA.
authors.forename: S
authors.initials: S
authors.lastname: Madisetti
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Asbeck
authors.affiliation: Department of Nanoscale Science and Engineering, University at Albany-State University of New York, Albany, New York 12222, USA.
authors.forename: S
authors.initials: S
authors.lastname: Oktyabrsky
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Kummel