A 365-nm UV LED was fabricated based on embedded nanoporous AlGaN distributed Bragg reflectors (DBR) by electrochemical etching. The porous DBR had a reflectance of 93.5% at the central wavelength of 365 nm; this is the highest value of porous AlGaN DBRs below 370 nm which has been reported so far. An innovative two-step etching method with a SiO₂ sidewall protection layer (SPL) was proposed to protect the n-AlGaN layer and active region of UV LED from being etched by the electrolyte. The DBR-LED with SPL showed 54.3% improvement of maximal external quantum efficiency (EQE) and 65.7% enhancement of optical power at 100 mA without any degeneration in electrical properties, compared with the un-etched standard LED sample. This work has paved the way for the application of electrically-pumped UV LEDs and VCSELs based on nanoporous AlGaN DBRs.

We use a p ⁺ -AlInGaN strained interlayer to form ohmic contact between p-GaN and indium tin oxide, and achieve a specific contact resistance of 6.06 × 10 ⁻² Ω · cm ² , similar to that with a p ⁺ -InGaN interlayer. When applied in a 365 nm UV LED, it shows a 0.5 V reduction of working voltage and an 18.1% enhancement of light output power, compared with those of the reference LED. Furthermore, the light output power is 12.8% higher than that of a LED with a p ⁺ -InGaN interlayer. These results indicate that a strained p-AlInGaN interlayer is a favorable choice for UVA LEDs.