Influence of annealing treatment on the luminescent properties of Ta:β-Ga₂O₃ single crystal

Ta⁵⁺ doped β-Ga₂O₃ single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400℃ for 20 hours. The transmittance spectra, photoluminescence (PL), x-ray irradiation spectra, and PL decay profiles of the samples were measured at room temperature. The relevant results show that the optical transmittance of the samples annealed in the air or nitrogen gas was improved. By drawing the (ahv)²-hv graph, it can be seen that the band gap decreased after being annealed in the air, but increased in nitrogen gas. The PL spectra and x-ray irradiation spectra show that the luminescent intensity of the sample annealed in the air increased substantially, while decreased for the sample annealed in nitrogen. The PL decay time of the Ta:β-Ga₂O₃ annealed in the air increased significantly compared with that of the Ta:β-Ga₂O₃ sample without annealing, but the tendency after annealing in nitrogen gas was opposite.