Intrinsic Point Defects, Charge Neutrality, and Self-Doping in β-Ga₂O₃

We present a holistic method to determine intrinsic doping and identify the charge neutrality point of semiconductors using density functional theory. By relying strictly on the physical meaning of charge neutrality point we are able to more accurately determine the Fermi level of semiconductors doped with native point defects at temperature, especially when coupled to chemical potentials for the defect-energy calculations that are coupled to the specific stoichiometry of the crystal. This method is applied to β-Ga₂O₃, a wide bandgap semiconductor known for being a deep UV transparent conducting oxide. Using hybrid-functional based DFT, we examine the tunability of the Fermi level and intrinsic point defects with respect to composition for the two extremes of crystal growth: instantaneous quenching and adiabatic cooling. In the case of stoichiometric β-Ga₂O₃ we’ve found the traditional method to computationally determine charge neutrality points to not properly describe the intrinsic Fermi level, whereas our method does. Our results suggest an explanation for the n-type nature of the grown crystals based on the grown stoichiometry and the imperfections present.