Positron Annihilation Spectroscopy of Vacancy Type Defects in Electron Irradiated β‐Ga2O3

Positron annihilation spectroscopy is applied to high‐quality β‐Ga2O3 [010] oriented 5 μm thick epilayer before and after electron irradiation to calculate absolute vacancy concentrations. Room temperature irradiated is carried out with 2.5 MeV electrons to a dose of 1.9 × 1019 cm−2 to generate high concentrations of vacancies. Both oxygen and gallium vacancies are generated. The vacancy‐sensitive depth‐dependent S‐parameter and the positron diffusion length were measured to determine vacancy concentrations. The positron diffusion length dropped from 101 ± 2 nm to 47 ± 2 nm while the S‐value in the epilayer rose 2.1 ± 0.3%. The positron annihilation spectroscopies (PAS) results on the irradiated film, in comparison with unirradiated as‐grown high‐quality bulk single crystals, are used to obtain for the first time a quantitative estimate of the defect concentration from the S‐parameter for various samples. The −3 charge state of gallium vacancies is taken into account. PAS results on irradiated silicon are shown for contrast, to illustrate the complications in β‐Ga2O3 introduced by a significant orientation dependence and, likely, the presence of hydrogen.