Synthesis, lattice structure, and band gap of ZnSnN2

Abstract

We report the synthesis of a direct gap semiconductor, ZnSnN 2 , by a plasma-assisted vapor-liquid-solid technique. Powder X-ray diffraction measurements of polycrystalline material yielded lattice parameters in good agreement with predicted values. Photoluminescence efficiency at room temperature was observed to be independent of excitation intensity between 10 3 and 10 8 W/cm 2 . The band gap was measured by photoluminescence excitation spectroscopy to be 1.7 ± 0.1 eV. The range of direct band gaps for the Zn(Si,Ge,Sn)N 2 alloys is now predicted to extend from 4.5 to 1.7 eV, opening up this little-studied family of materials to a host of important applications.

Charge-neutral disorder and polytypes in heterovalent wurtzite-based ternary semiconductors: The importance of the octet rule

“…19 Because the P na2 1 and P mc2 1 structures are superlattices of the wurtzite structure, distorted by deviations from the ideal wurtzite atomic positions, their x-ray diffraction spectra should be characterized by specific superlattice peaks absent in the disordered structure, and peak splittings arising from deviations in the ratios of the lattice parameters from the ideal wurtzite ratios. The strongest of the predicted superlattice peaks are the (101) peak for P na2 1 ordering and the (111) peak for P mc2 1 ordering, as shown in Fig.…”

“…19. Briefly, the method involved the exposure to a nitrogen plasma of a Zn-Sn melt held at 485 • C. The grown material was a polycrystalline layer, approximately 300 nm thick, covering most of an area approximately 0.5 cm in diameter.…”

“…It was suggested that controlling the degree of this disorder would allow the controlled variation of the band gap from 1 to 2 eV. 15 However, measurement of the band gap by photoluminescence excitation spectroscopy 19 of material that looked wurtzitic in x-ray diffraction gave a gap in close agreement with accurately predictive quasiparticle band structure calculations for perfectly ordered P na2 1 crystals, using experimentally determined lattice parameters. 13,26 The main question we address in this paper is how to reconcile these seemingly contradictory observations.…”

“…13 The synthesis of ZnSnN 2 in particular has fueled interest in its use for solar photovoltaics, especially because this material is composed solely of earthabundant elements. [14][15][16][17][18][19][20][21] As is the case for the zincblendebased ternaries, the type of ordering and the possibility of order-disorder transitions in the wurtzite-based ternaries are of fundamental as well as practical interest. For ZnGeN 2 and ZnSnN 2 the parent binary materials are the III-nitrides, and the parent binary phase is wurtzite.…”

“…26.) Synthesis of ZnSnN 2 was first reported in 2012 by molecular beam epitaxy 14 , soon afterward by radio frequency (RF) sputter deposition 16,17 and by a vapor-liquid-solid method 19 , and more recently by direct current (DC) magnetron sputtering 21 . All four methods yielded wurtzitic x-ray diffraction spectra, implying considerable disorder on the cation sublattices that was presumed to involve many violations of the octet rule.…”