Electron irradiation effects on the optical properties of Hf- and Zn-doped β-Ga2O3

Optical and electrical properties of Hf- and Zn-doped β-Ga2O3 samples, which are n-type and insulating, respectively, were altered via high-energy electron irradiation at 2.5 or 0.5 MeV. The β-Ga2O3:Hf samples irradiated with 2.5 MeV electrons experienced a color change from blue to yellow and a large drop in conductivity, attributed to the creation of gallium vacancies, which compensate donors. This irradiation resulted in the absence of free carrier absorption and the presence of Cr3+ photoluminescence (PL). PL mapping prior to irradiation revealed optically active ZnO precipitates that formed during the growth of β-Ga2O3:Zn. These precipitates have a 384 nm (3.23 eV) stacking fault emission in the core; in the outer shell of the precipitate, the PL blue-shifts to 377 nm (3.29 eV) and a broad defect band is observed. After 0.5 MeV electron irradiation, the defect band broadened and increased in intensity. The blue PL band (435 nm) of β-Ga2O3 was enhanced for both Hf- and Zn-doped samples irradiated with 0.5 MeV. This enhancement is correlated with an increase in oxygen vacancies.