Fig. 1

Simulation of the designed structures of DUV LED with and without SEDL. a A schematic of DUV LED structure with chirped SEDL. The 20-period SEDL with different Al compositions is inserted between the n-type AlGaN layer and the AlGaN current spreading cladding layer. b Whole band structure of conventional sample (a) without SEDL. The highlighted area refers to the designate region where the SEDL is to be inserted. c Band structure of the SEDL of sample (b), which is the 20-period homogeneous Al0.5Ga0.5N/Al0.65Ga0.35N superlattice. Each layer of the SEDL is 1 nm. d Band structure of the SEDL of sample (c), which is four sets of the 5-period declining Al-content SEDL superlattice with different high-Al-content layers, namely 0.7, 0.65, 0.6, and 0.55. e Band structure of the SEDL of sample (d), which is four sets of the 5-period ascending Al-content SEDL superlattice with different high-Al-content layers, namely 0.55, 0.6, 0.65, and 0.7