Dielectric function and electronic structure of nondegenerate rocksalt ScN: Spectroscopic ellipsometry and GW calculations

In this work, we determine the dielectric function of ScN in a spectral range from 0.9 to 6.4 eV by spectroscopic ellipsometry from nondegenerate doped, bulk-like samples. Several models are applied to the obtained dielectric functions yielding the main critical-point transition energies. These results are compared with state-of-the-art computations, where the band structure of ScN is calculated using Heyd-Scuseria-Ernzerhof (HSE06) hybrid functionals and quasiparticle corrections in the G 0 W 0 approach. Furthermore, the dielectric function of ScN is derived from the computed band structure by solving the Bethe-Salpeter equation to account for electron-hole-pair interactions. We find exceptional agreement between computed and experimentally determined dielectric functions, where discrete excitons are not observed experimentally. We extrapolate an intrinsic direct band gap of ( 2.182 ± 0.004 ) eV and an intrinsic indirect band gap of ( 1.08 ± 0.02 eV ) by taking into account many-body effects, while higher energy critical-point transition energies of Γ -point transitions are averaged over all samples, yielding E Γ = ( 3.853 ± 0.006 ) eV and E Γ ′ = ( 5.21 ± 0.02 ) eV . Critical-point transitions in the computed band structure, although, deviate from the experimental ones due to the omission of electron-hole-interaction, where the deviation increases with increasing energy. The dielectric limit of the electronic system is determined as ɛ ∞ = 8.38 ± 0.04 from experiment, where the computed dielectric function reveals almost the same value ( ɛ ∞ = 8.33 ). Along with other previous publications, we conclude that solving the Bethe-Salpeter equation is indispensable for the computation of the dielectric function of semiconductors even in the absence of discrete excitons.