Universal role of dopant-VGa complexes induced carrier suppression in Si/Ge/Sn/Zr-doped <i>β</i> -Ga2O3

The development of high-performance β-Ga2O3 electronics is critically hindered by the fundamental limitation of self-compensation in n-type doping, which severely suppresses free carrier concentrations. To explore the microscopic mechanism of this effect, we systematically investigate the four n-type dopants (Si, Sn, Ge, and Zr) in β-Ga2O3, combining first-principles calculations and experimental investigations. The calculation results show that the lower formation energies of SiGaVGa and SnGaVGa complexes compared to GeGaVGa and ZrGaVGa complexes lead to their higher concentrations and consequently stronger compensation in Si and Sn doping β-Ga2O3 under O-rich conditions. Oxygen annealing induces a severe compensation effect, as consistently validated by Hall effect and non-contact eddy current measurements. Beyond this universal mechanism, we further identify that the carrier compensation predominantly occurs near the surface, manifesting as a dramatic drop in near-surface carrier concentration and a sharp increase in contact resistivity in Sn-doped β-Ga2O3. Furthermore, photoluminescence spectra exhibit distinct green emission (∼2.5 eV), confirming the formation of the predicted deep-level defects SnGaVGa. This work reveals the microscopic compensation mechanism, providing vital theoretical and experimental insights for optimizing n-type β-Ga2O3 conductivity.