Is p-Type Doping in SeO2 Feasible?
The significance of p-type transparent oxide semiconductors (TOS) in the semiconductor industry is paramount, driving advancements in optoelectronic technologies for transparent electronic devices with unique properties. The recent discovery of p-type behavior in SeO2 has stirred both interest and confusion in the scientific community. In this Letter, we employ density functional theory calculations to unveil the intrinsic insulating characteristics of SeO2, highlighting substantial challenges in carrier doping. Our electronic structure analyses indicate that the Se 5s2 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 in SeO2 limits its potential as a high-mobility p-type TOS. Defect calculations demonstrate that all intrinsic defects in SeO2 exhibit deep transition levels within the bandgap. The Fermi level consistently resides in the mid-gap region, regardless of synthesis conditions. Furthermore, deep intrinsic acceptors and donors exhibit negative formation energies in the n-type and p-type regions, respectively, facilitating their spontaneous formation and impeding external doping efforts. Thus, the reported p-type conductivity in SeO2 samples is unlikely intrinsic and is more plausibly attributed to reduced elemental Se, a well-known p-type semiconductor.