Institute of Fundamental Technological Research

Hybrid-density-functional-theory calculations are used to evaluate the structural and electronic properties and formation energies of N-doped β-Ga2O3. Altogether, eleven interstitial (Ni) and three substitutional (NOI,II,III) impurity positions are investigated. Since direct evidence of N2 formation following the annealing of Ga2O3 and ZnO matrixes is revealed experimentally earlier, four complexes comprising two N atoms are also considered. It is determined that substitutional nitrogen defects act as deep acceptors, whereas the interstitial defects and N2-like complexes act as deep donors. Under Ga-rich growth conditions, substitutional nitrogen defects exhibit lower formation energies, with NOII defects being the most favorable. Under Ga-poor conditions, interstitial defects are more energetically desirable for a wide Fermi energy range, with Ni9 defect being the most favorable. The formation of the N2-like considered here at solely interstitial positions is energetically very expensive regardless of growth conditions. Finally, the Ni9–NOI complex is the most desirable one under Ga-rich conditions. This knowledge can serve as a basis for the development of optimal doping strategies, potentially leading to improved performance in future β-Ga2O3-based electronic devices.

In this work, hybrid density functional theory calculations are used to evaluate the structural and electronic properties and formation energies of Si-doped β-Ga2O3. Overall, eight interstitial (Sii) and two substitutional (SiGa) positions are considered. In general, our results indicate that the formation energy of such systems is significantly influenced by the charge state of the defect. It is confirmed that it is energetically more favorable for the substitution process to proceed under Ga-poor growth conditions than under Ga-rich growth conditions. Furthermore, it is confirmed that the formation of SiGaI with a tetrahedral coordination geometry is more favorable than the formation of SiGaII with an octahedral one. Out of all considered interstitial positions, due to the negative formation energy of the Si +3 charge state at i8 and i9 interstitial positions over the wide range of Fermi energy, this type of defect can be spontaneously stable. Finally, due to a local distortion caused by the presence of the interstitial atom as well as its charge state, these systems obtain a spin-polarized ground state with a noticeable magnetic moment.