Ordering in the mixed ZnGeN2 -GaN alloy system: Crystal structures and band structures of ZnGeGa2N4 from first principles

Quaternary Wurtzitic Nitrides (1 – x)ZnGeN2–2xGaN (x = 0.02, 0.05): Disorder-Induced Band-Gap Narrowing and Potentiality as a Solar-Active Photocatalyst

“…Skachkov et al predicted by the supercell calculations for ZnGeN 2 that the band-gap reduction (Δ E g ) increases from 0.54 eV for the single exchange defect per 128-atom cell (corresponding to i = 0.03125) to 3.07 eV for the fully disordered case ( i = 0.5) as the fraction of the octet-rule-violating tetrahedra increases from 6/64 to 40/64. The Δ E g value of ∼0.4 eV attained finally for the current quaternary system was less pronounced compared to that expected for the hypothetical disordered ZnGeN 2 , while it was fairly close to the Δ E g value of 0.47 eV predicted for ZnGeGa 2 N 4 with an octet-rule-violating structure …”

“…Figure a shows the pseudoabsorption coefficient (α) of the ZGGN specimens, derived from the DRS data transformed by the Kubelka–Munk function. The corresponding plot of (α h ν) 2 versus h ν is shown in Figure b, considering that direct band gaps are expected for both end members , and ZnGeGa 2 N 4 . In our previous work, an abrupt decrease of the band gap ( E g ) from 3.42 eV for x = 0 to 3.04 eV for x = 0.10 was observed, and then E g scarcely decreased to 3.02 eV for x = 0.50, suggesting that the degree of cation disorder is already close to unity at x = 0.10, as expected from the XRD results.…”

“…The synthesized ZGGN possessed activity for photocatalytic water reduction and oxidation with H 2 evolution rates of 2.8–3.6 μmol/h and O 2 evolution rates of 100.4–126.6 μmol/h, and an overall water splitting under visible light of λ > 400 nm was demonstrated. Later, Lambrecht et al reported possible crystal structures and electronic structures for the ZGGN system with a corresponding x of 0.5 (ZnGeGa 2 N 4 ) on the basis of first-principles calculations. They showed somewhat unexpected results that the band gaps of two hypothetical octet-rule-obeying superlattices ( Pmn 2 1 and P 1 n 1) were found to be slightly larger than those of ZnGeN 2 and GaN, while a reduced band gap was predicted for another energetically costly octet-rule-violating superlattice.…”

Utilizing Site Disorder in the Development of New Energy-Relevant Semiconductors

“…55 Finally, the opportunity exists for a III−V/II−IV-V 2 alloy system such as ZnGeGa 2 N 4 , a 50−50 mixture of ZnGeN 2 and GaN. 95 Such systems are relatively unexplored, both theoretically and experimentally, and the impact of such alloying on optical and transport properties is not wellunderstood. Solid solutions of (ZnGeN 2 ) x −(GaN) luminescence excitation experiments.…”

“…ZnGeP 2 can be controllably disordered, resulting in absorption onsets from about 1−2 eV, as shown in Figure7, and may be a useful visible spectrum emitter 55. Finally, the opportunity exists for a III−V/II−IV-V 2 alloy system such as ZnGeGa 2 N 4 , a 50−50 mixture of ZnGeN 2 and GaN 95. Such systems are relatively unexplored, both theoretically and experimentally, and the impact of such alloying on optical and transport properties is not wellunderstood.…”