Effect of high-energy electron irradiation on the electronic properties of beta-gallium oxide

Irradiation with high-energy electrons (HEE) at cryogenic temperatures is a subtle tool for shaping matter. Unlike irradiation with heavy particles, e.g. protons, neutrons, or ions, HEE irradiation produces very low local damage generating only point defects in the lattice. In the interaction process, the primary high-energy electron transfers just enough energy to displace a lattice ion from its equilibrium lattice site. The concentration of induced vacancies can be precisely controlled through the irradiation dose. Since lattice defects can act as donor or acceptor states in semiconductors, electron irradiation enables accurately-controlled compensation of the electrically-active impurities which were introduced into the semiconductor crystal during growth. This article, presents a study of the evolution of the electronic properties of beta-gallium oxide during step-by-step compensation of initial n-type doping through controlled introduction of point defects (gallium vacancies) produced by a 2.5-MeV electron beam. Analysis is based on a set of electron paramagnetic resonance, photoluminescence and electrical transport data obtained as a function of temperature.