Ultraviolet vertical thin-film light-emitting diode.

Vertical thin-film light-emitting diode (VTF-LED) adopts a GaN thin-film structure that confines light via the top GaN-air and the bottom GaN-metal interfaces. Such interfaces provide significantly higher optical reflectivity to promote optical confinement. As the structures are cladding-less, VTF-LED can be processed from simpler epitaxial structures comprising a p-n junction and the multi-quantum wells, directly leading to facile fabrication and lower manufacturing costs. Here, we demonstrate a 310-nm-thick ultraviolet VTF-LED, where precise control of the etching technique ensures electrical and optical performance. The emission wavelength was 382.9 nm with a spectrum width of 12 nm. Compared to VTF-LEDs with a submicron structure, the subwavelength VTF-LEDs exhibit a decrease in the number of guided modes and achieve a 1.7 times enhancement in peak external quantum efficiency. Subwavelength VTF-LEDs have been confirmed as an effective method for improving the light extraction efficiency (LEE) of AlGaN-based LEDs.