Investigation of optical-output-power degradation in 365-nm UV-LEDs

Abstract

The dependence of UV-LED lifetime on threading dislocation density(TDD) was examined. UV-LED structures were grown on standard GaN template(TDD: 1×108/cm2) and ELO-GaN(TDD: 1×10 7/cm2), and lifetime testing was performed under a forward current of 500 mA at junction temperature(Tj) of 75°C. Lifetime of both LEDs were estimated as 17,600 h (standard GaN template) and 166,000 h (ELO-GaN), respectively. It was found that GaN underlying layer with TD-density of 1×107/cm2 is superior to that of 1×10 8/cm2 in terms of LED lifetime, despite no output power difference. Junction temperature (Tj) dependence of LED lifetime was investigated in use of standard GaN template(1×108/cm 2). Tj was varied from 311 K to 422 K. The activation energy was determined to be 0.36 eV. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.