A review on the reliability of GaN-based LEDs

We review the degradation mechanisms that limit the reliability of GaN-based light-emitting diodes (LEDs). We propose a set of specific experiments, which is aimed at separately analyzing the degradation of the properties of the active layer, of the ohmic contacts and of the package/phosphor system. In particular, we show the following: 1) Low-current density stress can determine the degradation of the active layer of the devices, implying modifications of the charge/deep level distribution with subsequent increase of the nonradiative recombination components; 2) high-temperature storage can significantly affect the properties of the ohmic contacts and semiconductor layer at the p-side of the devices, thus determining emission crowding and subsequent optical power decrease; and 3) high-temperature stress can significantly limit the optical properties of the package of high-power LEDs for lighting applications.