Indium Gallium Oxide Alloys: Electronic Structure, Optical Gap, Surface Space Charge, and Chemical Trends within Common-Cation Semiconductors.



Swallow, Jack EN, Palgrave, Robert G ORCID: 0000-0003-4522-2486, Murgatroyd, Philip AE, Regoutz, Anna ORCID: 0000-0002-3747-3763, Lorenz, Michael ORCID: 0000-0003-2774-6040, Hassa, Anna, Grundmann, Marius ORCID: 0000-0001-7554-182X, von Wenckstern, Holger, Varley, Joel B ORCID: 0000-0002-5384-5248 and Veal, Tim D
(2021) Indium Gallium Oxide Alloys: Electronic Structure, Optical Gap, Surface Space Charge, and Chemical Trends within Common-Cation Semiconductors. ACS applied materials & interfaces, 13 (2). 2807 - 2819.

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Abstract

The electronic and optical properties of (In<sub><i>x</i></sub>Ga<sub>1-<i>x</i></sub>)<sub>2</sub>O<sub>3</sub> alloys are highly tunable, giving rise to a myriad of applications including transparent conductors, transparent electronics, and solar-blind ultraviolet photodetectors. Here, we investigate these properties for a high quality pulsed laser deposited film which possesses a lateral cation composition gradient (0.01 ≤ <i>x</i> ≤ 0.82) and three crystallographic phases (monoclinic, hexagonal, and bixbyite). The optical gaps over this composition range are determined, and only a weak optical gap bowing is found (<i>b</i> = 0.36 eV). The valence band edge evolution along with the change in the fundamental band gap over the composition gradient enables the surface space-charge properties to be probed. This is an important property when considering metal contact formation and heterojunctions for devices. A transition from surface electron accumulation to depletion occurs at <i>x</i> ∼ 0.35 as the film goes from the bixbyite In<sub>2</sub>O<sub>3</sub> phase to the monoclinic β-Ga<sub>2</sub>O<sub>3</sub> phase. The electronic structure of the different phases is investigated by using density functional theory calculations and compared to the valence band X-ray photoemission spectra. Finally, the properties of these alloys, such as the n-type dopability of In<sub>2</sub>O<sub>3</sub> and use of Ga<sub>2</sub>O<sub>3</sub> as a solar-blind UV detector, are understood with respect to other common-cation compound semiconductors in terms of simple chemical trends of the band edge positions and the hydrostatic volume deformation potential.

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 11 Jan 2021 09:13
Last Modified: 03 Mar 2021 10:22
DOI: 10.1021/acsami.0c16021
Open Access URL: https://doi.org/10.1021/acsami.0c16021
URI: https://livrepository.liverpool.ac.uk/id/eprint/3113182