Reliability of deep UV LEDs

We report on reliability of deep UV (DUV) LEDs with wavelengths ranging from 235 nm to 310 nm. For longer wavelength DUV LEDs, the operation lifetime (50% decrease of output power) exceeds 5,000 hours. The current-voltage characteristics and the emission spectrum remain nearly unchanged during the degradation process. The degradation is sensitive to the operating temperature. The low frequency noise measured at low and high currents either did not depend on aging time or decreased. Possible degradation mechanisms involve the p-cladding layers and p-type contacts being responsible for the degradation. Improvements in light extraction and packaging that should increase the wall plug efficiency are expected to result in a low operating temperature and, hence, in a longer life time.