Theoretical and Experimental Investigations on Effects of Native Point Defects and Nitrogen Doping on the Optical Band Structure of Spinel ZnGa₂O₄

Abstract

Impurity 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.

p-Type Ultrawide-Band-Gap Spinel ZnGa2O4: New Perspectives for Energy Electronics

“…As mentioned before, according to previous literature [42][43][44][45][46] , the most plausible origin of p-type conductivity in ternary spinel ZnGa2O4 would be the anti-site ZnGa center, in contrast to normal binary oxides where it is generally ascribed to a cation vacancy or interstitial. In our case, undoped β-Ga2O3 and spinel ZnGa2O4 exhibit similar value of acceptor center activation energies (Ea) but still 100 times more free holes in ZnGa2O4 films.…”

“…with acceptor-like Zn 2+ (Td)-on-Oh antisite defects or donor-like Ga 3+ (Oh)-on-Td as . GaZn defects [42][43][44][45][46] .…”

Bipolar self-doping in ultra-wide bandgap spinel ZnGa2O4

“…In the same way, it has also been demonstrated a native high-temperature p-type conductivity for ZnGa2O4 thin films elaborated by MOCVD [43]. Although these observations and that a bunch of theoretical works deals with the issue [29,44,45], the actual phenomenological origin and mechanisms of the ZnGa2O4 spinel self-doping remain elusive. Here, we aim to shed light on the UWBG self-doping nature by a comparative analysis of native acceptor and donor spinel gallate by a range of spectroscopic and transport measurement techniques.…”

Effect of cation vacancies on the optical and dielectric properties of KSr2Nb5O15: A first‐principles study

“…Table shows the band gap, conduction band minimum (CBM), and valance band maximum (VBM) of KSN, KSN‐K, KSN‐Sr, and KSN‐K&Sr For KSN‐K, the band gap is 2.166eV and the VBM increases by 0.053 eV, for KSN‐Sr, the band gap is 1.990 eV and the VBM shifts by 0.145 eV, and for KSN‐K&Sr, the band gap is 2.060 eV and the VBM increases by 0.132 eV. When there are cation vacancies, there is a strong effect on the KSN band gap, which decreases by 1.46%‐9.46%, indicating its good photoexcitation property . The electrons transfer easily mainly because the charge balance of the perfect KSN structure is defeated when there are vacancies exist.…”

“…When there are cation vacancies, there is a strong effect on the KSN band gap, which decreases by 1.46%-9.46%, indicating its good photoexcitation property. 29 The electrons transfer easily mainly because the charge balance of the perfect KSN structure is defeated when there are vacancies exist. The band gap of KSN-Sr is the narrowest, which means the electrons transit the easiest.…”