Exploring effective p-type doping in Ga2O3 is crucial for both fundamental science and emerging applications. Recently, N and Zn elements have been shown to exhibit considerable contributions to effective p-type doping in 3D Ga2O3 experimentally and theoretically, whereas the studies of their doping behaviors in 2D Ga2O3 are rare. In this study, we investigate the possibilities of N and Zn elements to achieve effective p-type doping, manifesting in the introduction of shallow acceptor levels typically less than 0.5 eV in 2D Ga2O3 using first-principles calculations with the generalized gradient approximation + U method. The calculated defect formation energies suggest that the N-doped 2D Ga2O3 structures are more easily formed under Ga-rich conditions, while the Zn-doped structures are more readily generated under O-rich conditions. Moreover, the introduced N and Zn atoms preferentially incorporate on the threefold coordinated OII and pyramidally coordinated GaI sites, accompanying with N3− and Zn2+ oxidation states in 2D Ga2O3, respectively. In particular, the electronic structures indicate that the occupied N-2p and semi-occupied Zn-3d orbitals produce shallow hole levels ranging from 0.09 to 0.33 eV, demonstrating that N and Zn atoms can behave as effective p-type dopants in 2D Ga2O3. The magnetic moments for N- and Zn-doped 2D Ga2O3 are 1.00 μB due to the doping of one hole, where the magnetic moments can be mainly attributed to the N atom and the nearest O atoms, respectively. Our work may offer theoretical guidance for the design of p-type 2D Ga2O3 materials and shed light on its potential optoelectronic and magnetic applications.

The magnetic and electronic properties of boron-doped SrTiO₃ have been studied by first-principles calculations. We found that the magnetic ground states of B-doped SrTiO₃ strongly depended on the dopant-dopant separation distance. As the dopant–dopant distance varied, the magnetic ground states of B-doped SrTiO₃ can have nonmagnetic, ferromagnetic or antiferromagnetic alignment. The structure with the smallest dopant-dopant separation exhibited the lowest total energy among all configurations considered and was characterized by dimer pairs due to strong attraction. Ferromagnetic coupling was observed to be stronger when the two adjacent B atoms aligned linearly along the B-Ti-B axis, which could be associated with their local bonding structures. Therefore, the symmetry of the local structure made an important contribution to the generation of a magnetic moment. Our study also demonstrated that the O-Ti-O unit was easier than the Ti-B-Ti unit to deform. The electronic properties of boron-doped SrTiO₃ tended to show semiconducting or insulating features when the dopant–dopant distance was less than 5 Å, which changed to metallic properties when the dopant–dopant distance was beyond 5 Å. Our calculated results indicated that it is possible to manipulate the magnetism and band gap via different dopant–dopant separations.

Iron impurities are believed to act as deep acceptors that can compensate for the n-type conductivity in as-grown Ga₂O₃, but several scientific issues, such as the site occupation of the Fe heteroatom and the complexes of Fe-doped β-Ga₂O₃ with native defects, are still lacking. In this paper, based on first-principle density functional theory calculations with the generalized gradient approximation approach, the controversy regarding the preferential Fe incorporation on the Ga site in the β-Ga₂O₃ crystal has been addressed, and our result demonstrates that Fe dopant is energetically favored on the octahedrally coordinated Ga site. The structural stabilities are confirmed by the formation energy calculations, the phonon dispersion relationships, and the strain-dependent analyses. The thermodynamic transition level Fe³⁺/Fe²⁺ is located at 0.52 eV below the conduction band minimum, which is consistent with Ingebrigtsen’s theoretical conclusion, but slightly smaller than some experimental values between 0.78 eV and 1.2 eV. In order to provide direct guidance for material synthesis and property design in Fe-doped β-Ga₂O₃, the defect formation energies, charge transitional levels, and optical properties of the defective complexes with different kinds of native defects are investigated. Our results show that V_Ga and O_i can be easily formed for the Fe-doped β-Ga₂O₃ crystals under O-rich conditions, where the +3 charge state Fe_GaGa_i and −2 charge state Fe_GaO_i are energetically favorable when the Fermi level approaches the valence and conduction band edges, respectively. Optical absorption shows that the complexes of Fe_GaGa_i and Fe_GaV_Ga can significantly enhance the optical absorption in the visible-infrared region, while the energy-loss function in the β-Ga₂O₃ material is almost negligible after the extra introduction of various intrinsic defects.

Two-dimensional (2D) semiconductors have shown great prospects for future-oriented optoelectronic applications, whereas the applications of conventional 2D materials are significantly impeded by their low electron mobility (⩽200 cm² V⁻¹ s⁻¹). In this work, strain-mediated fluorine- and hydrogen-passivated 2D Ga₂O₃ systems (FGa₂O₃H) have been explored via using first-principles calculations with the Heyd–Scuseria–Ernzerh and Perdew–Burke–Ernzerhof functionals. Our results reveal a considerable high electron mobility of FGa₂O₃H up to 4863.05 cm² V⁻¹ s⁻¹ as the uniaxial tensile strain reaches 6%, which can be attributed to the enhanced overlapping of wave functions and bonding features. Overall, when applying uniaxial strain monotonously along the a(b) direction from compressive to tensile cases, the bandgaps of 2D FGa₂O₃H increase initially and then decrease, which originates from the changes of σ* anti-bonding in the conduction band minimum and π bonding states in the valence band maximum accompanying the lengthening Ga–O bonds. Additionally, when the tensile strain is larger than 8%, the stronger π bonding at the G point leads to an indirect-to-direct transition. Besides the highest electron mobility observed in n-type doped 2D FGa₂O₃H with 6% tensile strain, the electrical conductivity is enhanced and further elevated as the temperature increases from 300 K to 800 K. The variations of the absorption coefficient in the ultraviolet region are negligible with increasing tensile strain from 0% to 6%, which sheds light on its applications in high-power optoelectronic devices.