Impact of electron irradiation on semi-insulating and conductive β-Ga₂O₃ single crystals

The damage behavior and defect evolution in Si-doped and Fe-doped β-Ga₂O₃ crystals were investigated using an electron irradiation of 1 MeV at a dose of 1 × 10¹⁶ cm^-2 in conjunction with structural and optoelectronic characterizations. Distinct decline in electron spin resonance (ESR) signal with g = 1.96 and a UV luminesce of 375 nm were observed in Si-doped β-Ga₂O₃ due to the capture of free carriers by irradiation defects. As for the Fe-doped sample, both defect-related blue emission and Cr³⁺ impurity-related red luminescence underwent prominent suppression after electron irradiation, which can be correlated to the creation of V_O and V_Ga defects and the formation of non-radiative recombination. Noticeably, neither V_O- nor V_Ga-related ESR signals were detected in Fe-doped and Si-doped β-Ga₂O₃ irrespective of irradiation; g = 2.003 resonance was observed in Mg-doped β-Ga₂O₃ and it experienced remarkable augmentation after electron irradiation. We assigned the g = 2.003 peak to the V_Ga acceptor. Besides, although the Raman mode of 258 cm^-1 in Si-doped β-Ga₂O₃ has been suggested to be electron concentration dependent, no obvious change in peak intensity was observed before and after electron irradiation.