Relation of site disorder, band gap and localization in ZnGeN<sub>2</sub>
POSTER
Abstract
In ZnGeN2, site disorder is studied to manipulate the band gap to align with current technological deficiencies at green/amber emission wavelengths in light emitting diodes known as the “green gap,” while maintaining low lattice mismatch with GaN. We present cluster-based Monte Carlo simulations to evaluate site disorder in ZnGeN2 at short- and long-range. Converged configurations are relaxed in volume and lattice parameters through Density Functional Theory. Band gap-corrected hybrid calculations are used to obtain the electronic structure of the 1,024 atom supercells and structural and electronic parameters are then used in device modeling to study the effects of site disorder on quantum well design for light emitting diodes. We calculate nitrogen coordination and Bragg-Williams short- and long-range order parameters, respectively, to relate order and electronic structure and analyze state localization as a means of differentiating defect states from band gaps which remain ill-defined in disordered systems. In ZnGeN2, the non-isovalent character of the disordered species (Zn2+ and Ge4+) subjects the cation ordering to strong short-range order effects which influence band structure by decreasing the band gap relative to ordered ZnGeN2 across a wide range.
*This work was supported by the U.S. Department of Energy(DOE) under Contract No.DE-AC36-08GO28308 with the Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory. Funding was provided by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Buildings Technologies Office.
Publication:J. J. Cordell, J. Pan, A. C. Tamboli, G. J. Tucker and S. Lany. "Probing configurational disorder in ZnGeN2 using cluster-based Monte Carlo." Physical Review Materials (2021). J. J. Cordell, A. C. Tamboli, G. J. Tucker and S. Lany. "Role of cation disorder in carrier localization and density of states in ZnGeN2." arXiv preprint arXiv:2109.05062 (2021). J. J. Cordell, A. C. Tamboli, G. J. Tucker and S. Lany. "Band gap analysis and carrier localization in cation-disordered ZnGeN2." submitted.
