Is p-Type Doping in SeO₂ Feasible?

p-type transparent oxide semiconductors (TOSs) are significant in the semiconductor industry, driving advancements in optoelectronic technologies for transparent electronic devices with unique properties. The recent discovery of p-type behavior in SeO_2 has stimulated interest and confusion in the scientific community. In this Letter, we employ density functional theory calculations to reveal the intrinsic intrinsic insulating characteristics of SeO_2 and highlight the substantial challenges in carrier doping. Our electronic structure analyses indicate that the Se 5s^2 states are energetically positioned too low to effectively interact with the O 2p orbitals, resulting in a valence band maximum (VBM) primarily dominated by the O 2p orbitals. The deep and localized nature of the VBM of SeO_2 limits its potential as a high-mobility p-type TOS. Defect calculations demonstrate that all intrinsic defects in SeO_2 exhibit deep transition levels within the bandgap. Regardless of the synthesis conditions, the Fermi level consistently resides in the mid-gap region. Furthermore, deep intrinsic acceptors and donors exhibit negative formation energies in the n-type and p-type regions, respectively, facilitating spontaneous formation and impeding external doping efforts. Thus, the reported p-type conductivity in SeO_2 samples is unlikely to be intrinsic and is more plausibly attributable to reduced elemental Se, a well-known p-type semiconductor.