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 Al 0.25 Ga 0.75 N carrier-blocking layer showed a shoulder peak at ∼370 nm due to electron overflow into the p-Al 0.10 Ga 0.90 N 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 ∼520 nm was emitted from the AlGaN layers within the quantum wells.