We have investigated the dual role of interfacial defects in creating both nonradiative interface recombination and interface charge. Our studies are based on Ga2O3-GaAs interface structures with their unique properties such as low interface state density and radiative GaAs band-to-band recombination. The self-consistent analysis of the steady-state dependence of the spontaneous GaAs emission on excitation density provides all critical characteristics of interfacial defects simultaneously: the density of interface states, their capture cross sections, the interface recombination velocities, and the oxide charge.