Origins of Parasitic Emissions from 353 nm AlGaN-based Ultraviolet Light Emitting Diodes over SiC Substrates

The effects of p-GaN capping layer and p-type carrier-blocking layer on the occurrence of parasitic emissions from 353 nm AlGaN-based light emitting diodes (LEDs) have been investigated. LEDs without a p-type Al0.25Ga0.75N carrier-blocking layer showed a shoulder peak at similar to 370 nm due to electron overflow into the p-Al0.10Ga0.90N cladding layer and subsequent electron-hole recombination in the acceptor levels. Broad emission between 380 and 450 nm from LEDs having a p-GaN capping layer Was caused by luminescence at 420 nm from the p-GaN capping layer, which was optically pumped by 353 nm UV emission from the quantum wells. Broad, defect-related luminescence centered at similar to 520 nm was emitted from the AlGaN layers within the quantum wells.