AlGaN-based high power 340 nm vertical-chip ultraviolet LEDs

This is the authors' abstract. We don't add key points for this paper.

The 340 nm wavelength which lies near the UVA–UVB boundary, is vital for NADH-based biochemical assays and dermatological phototherapy. This work demonstrates a high-power 340 nm ultraviolet-A light-emitting diode grown on Si(111) substrate with a vertical thin-film flip-chip architecture. By incorporating a polarization-doped electron blocking layer featuring a linearly graded Al composition AlGaN, electron leakage is effectively suppressed while hole injection into the multiple quantum wells is significantly enhanced. Furthermore, V-pit engineering combined with an AlGaN interlayer design improves the carrier transport and suppresses nonradiative recombination. The as-fabricated 1.1 mm × 1.1 mm vertical-chip LEDs achieve a remarkably high light output power of 219.3 mW at 350 mA, corresponding to an external quantum efficiency of 17.6% and a wall-plug efficiency of 13.5%. The devices also exhibit excellent efficiency retention and long-term reliability, retaining over 70% of their initial output power after 5,000 hours of aging at 25 °C and 350 mA. This work represents a significant advancement toward the industrial adoption of high-power UVA LEDs grown on Si substrate.