Alloy-Free Band Gap Tuning across the Visible Spectrum
We present evidence, from theory and experiment, that ZnSnN2 and MgSnN2 can be used to match the band gap of InGaN without alloying—by exploiting cation disorder in a controlled fashion. We base this on the determination of S, the long-range order parameter of the cation sublattice, for a series of epitaxial thin films of ZnSnN2 and MgSnN2 using three different techniques: x-ray diffraction, Raman spectroscopy, and in situ electron diffraction. We observe a linear relationship between S2 and the optical band gap of both ZnSnN2 (1.12–1.98 eV) and MgSnN2 (1.87–3.43 eV). The results clearly demonstrate the correlation betweencontrolledheterovalentcationorderingandtheopticalbandgap,whichappliestoabroadgroupof emerging ternary heterovalent compounds and has implications for similar trends in other material properties besides the band gap.