Degradation analysis of Violet high power LEDs

With this work we report on the degradation of GaN 420nm high brightness LEDs. Devices have been subjected to constant current stress at 350mA at different temperatures. Results indicate that different ageing mechanisms take place: i) a steep variation in electrical and capacitance characteristics after the first few hours of operation, probably related to a reduction of activated doping in the p-type region caused by the flow of current ii) a substantial increase of the optical power in the low forward bias current region iii) a decrease of OP in the high current injection regime.