A physical explanation to the controversial Urbach tailing universality

Doping-related behavior divergence of some crystalline materials has raised doubts about Urbach tailing universality. In this paper, we infer the atomic scale interpretation of this divergence on the basis of experimental records and comparative studies. We focus on a widely known wurtzite structured crystal and find that Urbach tailing was inhibited once doping charged loci succeeded to establish local coordinated donors networks or so-called topological filaments. The case of doping-free and saturated ZnO networks unexpected Urbach tailing features has been discussed. All the observed behaviors confirm the Urbach tailing universality despite their controversial aspect.