Electronic structures and formation energies of pentavalent-ion-doped SnO2: First-principles hybrid functional calculations

We studied the electronic properties and relative thermodynamic stability of several pentavalent-ion (Ta, Nb, P, Sb, and I) doped SnO2 systems using first-principles hybrid density functional theory calculations, in order to evaluate their potential as transparent conducting oxides (TCOs). I-doped SnO2, though conductive, shows a narrowed optical band gap with respect to the undoped system due to the formation of gap states above the valence band. Nb-doped SnO2 forms localized impurity states below the conduction band bottom, suggesting that the Nb dopant exists as an Nb4+-like cation, which is consistent with the recent experimental finding of the formation of the impurity level below the conduction band bottom [Appl. Phys. Express 5, 061201 (2012)]. Ta- and Sb-doped SnO2 display n-type conductivity, high charge carrier density, and widened optical band gap. P-doped SnO2 shows similar n-type electronic properties with that of Sb- and Ta-doped systems, and thus P-doped SnO2 is proposed as a promising candidate TCO for further experimental validation.