Transport Across Heterointerfaces of Amorphous Niobium Oxide and Crystallographically Oriented Epitaxial Germanium.

Title Transport Across Heterointerfaces of Amorphous Niobium Oxide and Crystallographically Oriented Epitaxial Germanium.
Authors M.K. Hudait; M. Clavel; J.S. Liu; A. Ghosh; N. Jain; R.J. Bodnar
Journal ACS Appl Mater Interfaces
DOI 10.1021/acsami.7b06601
Abstract

Because of the high carrier mobility of germanium (Ge) and high dielectric permittivity of amorphous niobium pentoxide (a-Nb2O5), Ge/a-Nb2O5 heterostructures offer several advantages for the rapidly developing field of oxide-semiconductor-based multifunctional devices. To this end, we investigate the growth, structural, band alignment, and metal-insulator-semiconductor (MIS) electrical properties of physical vapor-deposited Nb2O5 on crystallographically oriented (100), (110), and (111)Ge epilayers. The as-deposited Nb2O5 dielectrics were found to be in the amorphous state, demonstrating an abrupt oxide/semiconductor heterointerface with respect to Ge, when examined via low- and high-magnification cross-sectional transmission electron microscopy. Additionally, variable-angle spectroscopic ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to independently determine the a-Nb2O5 band gap, yielding a direct gap value of 4.30 eV. Moreover, analysis of the heterointerfacial energy band alignment between a-Nb2O5 and epitaxial Ge revealed valance band offsets (?EV) greater than 2.5 eV, following the relation ?EV(111) > ?EV(110) > ?EV(100). Similarly, utilizing the empirically determined a-Nb2O5 band gap, conduction band offsets (?EC) greater than 0.75 eV were found, likewise following the relation ?EC(110) > ?EC(100) > ?EC(111). Leveraging the reduced ?EC observed at the a-Nb2O5/Ge heterointerface, we also perform the first experimental investigation into Schottky barrier height reduction on n-Ge using a 2 nm a-Nb2O5 interlayer, resulting in a 20× increase in reverse-bias current density and improved Ohmic behavior.

Citation M.K. Hudait; M. Clavel; J.S. Liu; A. Ghosh; N. Jain; R.J. Bodnar.Transport Across Heterointerfaces of Amorphous Niobium Oxide and Crystallographically Oriented Epitaxial Germanium.. ACS Appl Mater Interfaces. 2017;9(49):4331543324. doi:10.1021/acsami.7b06601

Related Elements

Germanium

See more Germanium products. Germanium (atomic symbol: Ge, atomic number: 32) is a Block P, Group 14, Period 4 element with an atomic weight of 72.63. Germanium Bohr ModelThe number of electrons in each of germanium's shells is 2, 8, 18, 4 and its electron configuration is [Ar] 3d10 4s2 4p2. The germanium atom has a radius of 122.5 pm and a Van der Waals radius of 211 pm. Germanium was first discovered by Clemens Winkler in 1886. In its elemental form, germanium is a brittle grayish white semi-metallic element. Germanium is too reactive to be found naturally on Earth in its native state. High Purity (99.999%) Germanium (Ge) MetalIt is commercially obtained from zinc ores and certain coals. It is also found in argyrodite and germanite. It is used extensively as a semiconductor in transitors, solar cells, and optical materials. Other applications include acting an alloying agent, as a phosphor in fluorescent lamps, and as a catalyst. The name Germanium originates from the Latin word "Germania" meaning "Germany."

Niobium

See more Niobium products. Niobium (atomic symbol: Nb, atomic number: 41) is a Block D, Group 5, Period 5 element with an atomic weight of 92.90638. Niobium Bohr ModelThe number of electrons in each of niobium's shells is 2, 8, 18, 12, 1 and its electron configuration is [Kr] 4d4 5s1. The niobium atom has a radius of 146 pm and a Van der Waals radius of 207 pm. Niobium was discovered by Charles Hatchett in 1801 and first isolated by Christian Wilhelm Blomstrand in 1864. In its elemental form, niobium has a gray metallic appearance. Niobium has the largest magnetic penetration depth of any element and is one of three elemental type-II superconductors (Elemental Niobiumalong with vanadium and technetium). Niobium is found in the minerals pyrochlore, its main commercial source, and columbite. The word Niobium originates from Niobe, daughter of mythical Greek king Tantalus.

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