Investigations on the p‑Type Formation Mechanisms of Group II and VII Elements and N‑Doped β‑Bi₂O₃

In this work, the feasibility of p- and n-type doping modifications in intrinsic n-type β-Bi2O3 via Group VII (F, Cl, Br, I) and Group II (Be, Mg, Ca, Sr) elements as well as N have been systematically investigated using first-principles hybrid functional calculations. Notably, the p-type modification mechanism in N-doped β-Bi2O3 has been extensively, carefully, and comparably explored and analyzed, in contrast to the famous N-doped ZnO case. It is found that the enhancement of the n-type conductivity in β-Bi2O3 by Group VII element doping is easily achieved, and F is the best n-type dopant candidate. However, achieving the transition from an unintentional n-type to a p-type semiconductor in β-Bi2O3 is very difficult via Group II element doping because of the stronger compensation effect from the intrinsic donor O1 vacancy defect and unintentional H interstitial (donor) as well as the self-compensation effects from the doping itself under thermal equilibrium growth conditions. Fortunately, it should be easier to dope and achieve the p-type conductivity in β-Bi2O3 using NO2 rather than these source gases, including N2, N2O, NO, and NH3 or Group II element doping under O-poor conditions. The substitutional defect NO2 is the most possible candidate for the p-type modification. However, because of the charge compensation effect, nonequilibrium conditions such as annealing under high temperatures may be essential in obtaining long-lasting p-type conductivity for β-Bi2O3. Understanding the different element doping effects on the p- or n-type conductivity in β-Bi2O3 can further facilitate relevant experimental preparation and application studies