However, for accurate material characterization, ZnGeN2 must be grown without GaN due to their similar optical and structural properties. ZnGeN2 is a potential green-to-amber emitter which can be integrated into existing GaN LED heterostructures due to structural similarity. The trends shown here may help to guide understanding of the synthesis and characterization of other heterovalent ternary nitride semiconductors as well as ZnGeN2. Growth of ZnGeN2 on a liquid Sn-Ge-Zn alloy at 758 degree C showed an increase in the tendency for cation ordering at a lower growth temperature, and resulted in hexagonal platelet-shaped crystals. Annealing disordered, low-temperature-grown ZnGeN2 at 850 degree C resulted in increased cation ordering. The degree of ordering, from fully disordered, wurtzite-like x-ray diffraction spectra to orthorhombic, with space group Pna21, increased with increasing growth temperature, as evidenced by the appearance of superstructure peaks and peak splittings in the diffraction patterns. Crystallites tended to be rod-shaped, with growth rates higher along the c-axis. Polycrystalline ZnGeN2 was grown by exposing solid Ge to Zn and NH3 vapors at temperatures between 758 degree C and 914 degree C. Here the effects of growth and processing conditions on the ordering of the ZnGeN2 cation sublattice were investigated using x-ray diffraction and Raman spectroscopy. ZnGeN2 and other heterovalent ternary semiconductors have important potential applications in optoelectronics, but ordering on the cation sublattice, which can affect the band gap, lattice parameters, and phonons, is not yet well understood.
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