Alloy-Free Band Gap Tuning across the Visible Spectrum

• Published in: Physical review letters Vol. 122; no. 25; p. 256403
• Main Authors: Makin, Robert A, York, Krystal, Durbin, Steven M, Senabulya, Nancy, Mathis, James, Clarke, Roy, Feldberg, Nathaniel, Miska, Patrice, Jones, Christina M, Deng, Zihao, Williams, Logan, Kioupakis, Emmanouil, Reeves, Roger J
• Format: Journal Article
• Language: English
• Published: United States American Physical Society 27-06-2019
• Subjects: Cations; Electron diffraction; Energy gap; Indium gallium nitrides; Long range order; Material properties; Order parameters; Raman spectroscopy; Thin films; Visible spectrum; X-ray diffraction
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.122.256403

We present evidence, from theory and experiment, that ZnSnN_{2} and MgSnN_{2} 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 ZnSnN_{2} and MgSnN_{2} using three different techniques: x-ray diffraction, Raman spectroscopy, and in situ electron diffraction. We observe a linear relationship between S^{2} and the optical band gap of both ZnSnN_{2} (1.12-1.98 eV) and MgSnN_{2} (1.87-3.43 eV). The results clearly demonstrate the correlation between controlled heterovalent cation ordering and the optical band gap, which applies to a broad group of emerging ternary heterovalent compounds and has implications for similar trends in other material properties besides the band gap.