Tuning the Electronic Band Gap of Oxygen-Bearing Cubic Zirconium Nitride: c-Zr_3–x(N_1–xO_x)₄

Research has shown that group IVB nitrides have a narrow direct electronic band gap, but there have been few investigations into the dependence of the electronic band gap on cation defects and whether tuning the electronic band gap is possible by controlling the level of substitutional oxygen in c-Zr3–x(N1–xOx)4. We use a combination of soft X-ray spectroscopy and density functional theory to study the electronic structure and determine the electronic band gap as well as the exciton binding energy of an oxygen-bearing defect zirconium nitride, c-Zr2.86(N0.88O0.12)4, and oxygen-free hafnium nitride, c-Hf3N4. Moreover, we extend our structural model to consider the dependence of the electronic band gap on oxygen substitution in c-Zr3–x(N1–xOx)4. The results suggest that the electronic band gap can be precisely controlled between 1.47 and 1.84 eV (674–844 nm) by adjusting the stoichiometry, without adversely affecting the electronic structure. The exciton binding energy of c-Zr2.86(N0.88O0.12)4 is estimated to be 37 meV, much larger than current materials being used (GaAs). This larger exciton binding energy combined with both the direct narrow electronic band gap and stable electronic structure demonstrates that this material is an ideal candidate to replace currently used materials, such as GaAs, in infrared light-emitting diode applications.