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Optical Spectroscopy of Dopants and Defects in Gallium Oxide
Get PDFThis work examines the effects of dopants on single crystals of gallium oxide (β-Ga2O3) through photoluminescence, Fourier transform infrared, ultraviolet and visible spectroscopy, and Hall effect measurements.Key findings include the observation that Cr3+ photoluminescence is prominent in insulating samples but weak in n-type samples. High-energy electron irradiation of n-type β-Ga2O3 created gallium vacancies, leading to significant changes in color and conductivity, with a notable suppression of free-carrier absorption and the emergence of Cr3+ emissions.Further investigation of Cr and Zr co-doped β-Ga2O3 samples revealed that despite a high carrier concentration, and therefore a Fermi level within the conduction band, Cr3+ absorption and emissions were still observable. This suggests that the Cr acceptor level may reside within the conduction band. The Cr3+ PL was quenched compared to that of insulating samples. This quenching is likely due to the free carriers in the conduction band, which introduces additional non-radiative recombination pathways.Spatially resolved PL and Raman mapping were instrumental in identifying specific defect features, such as bright emitter centers associated with Si-CH compounds. Moreover,these techniques unveiled optically active precipitates, including ZnO and Cu2O, in doped β-Ga2O3 samples