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Theoretical and Experimental Investigations on Effects of Native Point Defects and Nitrogen Doping on the Optical Band Structure of Spinel ZnGa2O4
journal contribution
posted on 2018-02-19, 00:00 authored by Yuguo Xia, Ting Wang, Xiaozhou Zhao, Xiuling Jiao, Dairong ChenImpurity
states in semiconductors are so important for optical related properties
that understanding the role of native and imported defects is essential
to design highly active semiconductors. Here, the structural and electronic
properties of ZnGa2O4 with native atomic substitution,
oxygen vacancies, and imported N doping are first investigated by
first-principles calculations. It is demonstrated that native atomic
substitution is energetically unfavorable and the most stable existence
forms for N doping and O vacancies are N1– and O2+ states in most cases under various chemical environments.
The band structures and density of states reveal that the photochemical
property is significantly enhanced only by 2Ns doping with
a great increase of valence band maximum relative to the Fermi level,
whereas single-N atom doping or import of O vacancies or simultaneous
import of N doping and O vacancies just generates impurity states
in the band gaps. Moreover, experimental characterizations including
X-ray photoelectron spectroscopy and diffuse reflectance spectroscopy
spectra confirm the above theoretical results, and optical calculations
further illustrate the effects of defects for light absorption. Our
results will be helpful to understand the effects of native point
defects and external nitrogen doping on spinel ZnGa2O4 and design its band gap with desired optical properties.