Highly Transparent p-AlGaN-Based (326-341 nm)-Band Ultraviolet-A Light-Emitting Diodes on AlN Templates: Recent Advances and Perspectives

The epitaxial growth of transparent p-AlGaN-based ultraviolet-A (UVA), light-emitting diodes (LEDs) may solve the problems of UVA light absorption through the GaN buffers and p-GaN contact layers at (326-341 nm)-band emission, respectively. Herein, first, an idea of conventional n-AlGaN buffer layer (BL) and n-AlGaN electron source layer (ESL) for the suppression of threading dislocation density (TDD) and enhancement of internal quantum efficiency (IQE) of UVA emitters, using low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE) is attempted. As a result, the total-TDDs is reduced from approximate to 3 x 10(9) cm(-2) to approximate to 1 x 10(9) cm(-2) in the n-AlGaN ESL of a 326 nm-band UVA multiquantum-wells (MQWs), and IQE is also improved from 30% to 52% at room temperature (RT). Second, an idea of Si-doped n-AlGaN Superlattices (SLs)-based BL, using LP-MOVPE is challenged. Subsequently, a record IQE of 56% at RT and high crystal quality in 341 nm-band UVA MQWs are observed. Finally, using a well thickness approximate to 2 nm in SLs-based UVA MQWs, the light power and external quantum efficiency (EQE), respectively, are remarkably enhanced from 3.5 mW and 0.5% to 7.5 mW and 1.4% on wafer in 341 nm-Band UVA LED. The perspective for the improvements of UVA emitter's performances is also discussed.

Automated summary

In this study, p-AlGaN-based UV-A light-emitting diodes were grown epitaxially in order to solve the problem of light absorption. The use of LP-MOVPE technology allowed for the reduction of threading dislocation density and improvement of internal quantum efficiency, resulting in enhanced performance of the UV-A emitters.