Growth of rock-salt MgO–NiO–ZnO films: Relationship between lattice constant and composition

Deep-ultraviolet light-emitting diodes (DUV-LEDs) have emerged as eco-friendly alternatives to mercury lamps for various applications. This study explores MgO–NiO–ZnO alloy semiconductors as potential materials for DUV-LEDs, offering advantages over conventional AlGaN-based systems. MgO–NiO–ZnO films with varying compositions were grown using mist chemical vapor deposition (mist-CVD) and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and UV–visible spectroscopy. A single-phase rock-salt structure was obtained for ZnO mole fractions of up to 0.26, whereas phase separation occurred at higher levels of ZnO content. The lattice constant–composition relationship followed Vegard’s law, suggesting that MgO–NiO–ZnO films with a composition of Mg x (Ni 0.67 Zn 0.33 ) 1− x O could achieve lattice matching with MgO substrates. The band gaps of rock-salt MgO–NiO–ZnO, determined based on spectral transmittance measurements, ranged from 5.4 eV to 5.8 eV and increased with MgO content. These band gap values are sufficient for DUV-LED applications. This study provides crucial insights into MgO–NiO–ZnO alloy semiconductors, paving the way for the development of more efficient and strain-free DUV-LEDs. • MgO–NiO–ZnO films of various compositions were grown via mist-CVD. • The maximum ZnO mole fraction of single-phase rock-salt MgO–NiO–ZnO films was 0.26. • The lattice constant of rock-salt MgO–NiO–ZnO followed Vegard’s law. • The band gap of rock-salt MgO–NiO–ZnO increased 5.4–5.8 eV with MgO content.