May 8, 2018

Sapphire substrate sidewall shaping of deep ultraviolet light-emitting diodes by picosecond laser multiple scribing

We employ picosecond laser multiple scribing to fabricate oblique sidewalls of AlGaN-based deep ultraviolet light-emitting diode (LED) chips for enhanced light extraction. The multiple scribing lines in the sapphire substrate are intentionally aligned to guide the wafer to be diced along oblique sidewalls with designed angles. Compared with a conventional LED chip having vertical sidewalls, one with sidewalls inclined at 60° exhibits a 13.8% higher light output power at 50 mA without any deterioration of the laser-induced electrical characteristics. Finite-difference time-domain simulation reveals the optimized sidewall inclination angle and indicates that the inclination of the sidewall is effective for TM-polarized light extraction.


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