title: Epitaxial Growth of MgxCa1-xO on GaN by Atomic Layer Deposition.
abstract: We demonstrate for the first time that a single-crystalline epitaxial MgxCa1-xO film can be deposited on gallium nitride (GaN) by atomic layer deposition (ALD). By adjusting the ratio between the amounts of Mg and Ca in the film, a lattice matched MgxCa1-xO/GaN(0001) interface can be achieved with low interfacial defect density. High-resolution X-ray diffraction (XRD) shows that the lattice parameter of this ternary oxide nearly obeys Vegard's law. An atomically sharp interface from cross-sectional transmission electron microscopy (TEM) confirmed the high quality of the epitaxy. High-temperature capacitance-voltage characterization showed that the film with composition Mg0.25Ca0.75O has the lowest interfacial defect density. With this optimal oxide composition, a Mg0.25Ca0.75O/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility (MOS-HEMT) device was fabricated. An ultrahigh on/off ratio of 1012and a near ideal SS of 62 mV/dec were achieved with this device.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Xiabing
authors.initials: X
authors.lastname: Lou
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47906, United States.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Sang Bok
authors.initials: SB
authors.lastname: Kim
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47906, United States.
authors.forename: Sami
authors.initials: S
authors.lastname: Alghamdi
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Xian
authors.initials: X
authors.lastname: Gong
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Feng
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Xinwei
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47906, United States.
authors.forename: Peide D
authors.initials: PD
authors.lastname: Ye
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Roy G
authors.initials: RG
authors.lastname: Gordon
keywords: Epitaxy; GaN; MOS-HEMT; dielectric; magnesium calcium oxide