Modification of β-gallium oxide electronic properties by irradiation with high-energy electrons

We present a study of the modifications of the electronic properties of β-gallium oxide crystals by 2.5-MeV electron irradiation. This type of irradiation produces exclusively local point defects in Ga2O3, predominantly gallium vacancies, which act as acceptor centers. Starting with a highly n-doped sample, we establish a quantitative linear relation between the irradiation dose and the concentration of generated acceptor centers. This gives the possibility to tune the Fermi level position within the bandgap by choosing an appropriate irradiation dose. At high doses, with a very deep position of the Fermi level, the n-type sample becomes compensated, reaching a semi-insulating state. The downward shift of the Fermi level with irradiation allows us to reveal the presence of latent impurities of transition metals (like Cr and Fe), which are inactive in electron paramagnetic resonance and luminescence spectra of pristine samples. This study confirms the potential of electron irradiation as a tool for tailoring the electronic properties of gallium oxide.