Fig. 1. Epitaxial structure of deep ultraviolet LED

Fig. 2. Physical picture of the chip

Fig. 3. Physical photo of aging test samples

Fig. 4. Optical power of LEDs with different Al-component QB structures before and after aging

Fig. 5. Normalised optical power with time curves of LEDs with different Al-component QB structures

Fig. 6. Optical power of LEDs with different Al-component EBL structures before and after aging

Fig. 7. Normalised optical power with time curves of LEDs with different Al-component EBL structures

Fig. 8. Optical power of LEDs before and after aging of different table surface areas

Fig. 9. Normalised optical power with time curves of LEDs with different table surface areas

Fig. 10. Variation curvesoptical power and normalised optical power with aging time under different aging temperatures of LED

Fig. 11. Electroluminescence spectra before and after aging at different temperatures (40 mA test) of 60 ℃ and 85 ℃constant temperature aging，respectively

Fig. 12. I‑V curves (semi-logarithmic coordinates) before and after aging at different temperatures of 60 ℃ and 85 ℃ constant temperature aging，respectively

Fig. 13. I‑V curves (linear coordinates) before and after aging at different temperatures of 60 ℃and 85 ℃constant temperature aging，respectively

Fig. 14. Variation curves of optical power and normalised optical power with aging time under different aging currents of LEDs

Fig. 15. Electroluminescence spectra before and after aging for different currents (40 mA test) of 40 mA，120 mA and 160 mA，respectively

Fig. 16. I‑V curves (semi-logarithmic coordinates) before and after aging with different currents of 40 mA，120 mA and 160 mA，respectively

Fig. 17. I‑V curves (linear coordinates) before and after aging with different currents of 40 mA，120 mA and 160 mA，respectively

Fig. 18. The curves fitted to the variation of normalised optical power with time for different aging temperatures

Fig. 19. The curves fitted to the variation of normalised optical power with time for different aging currents