GaN-based LEDs: State of the art and reliability-limiting mechanisms

This paper reviews the main characteristics of state-of-the art high-brightness light-emitting diodes (LEDs), and the mechanisms responsible for the degradation of these devices. After a description of the structure, advantages and limits of power LEDs, we describe the following, relevant, degradation mechanisms: (i) the degradation of the active region of the devices, due to the generation of non-radiative defects and/or of shunt leakage paths; (ii) the worsening of the optical properties of the package and phosphor, which may induce a gradual degradation of the optical signal emitted by the devices; (iii) the catastrophic failure due to electrical overstress (hot-plugging) and to ESD events. The results described within this paper are critically compared to the data presented in the literature, quoted in the list of references.