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

摘要

The dependence of UV-LED lifetime on threading dislocation density(TDD) was examined. UV-LED structures were grown on standard GaN template(TDD: 1 x 10~8/cm~2) and ELO-GaN(TDD: 1 x 10~7/cm~2), and lifetime testing was performed under a forward current of 500 mA at junction temperature(T_j) of 75℃. 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 x 10~7/cm~2 is superior to that of 1 x 10~8/cm~2 in terms of LED lifetime, despite no output power difference. Junction temperature (T_j) dependence of LED lifetime was investigated in use of standard GaN template(1 x 10~8/cm~2). T_j was varied from 311 K to 422 K. The activation energy was determined to be 0.36 eV.