Degradation of InGaN lasers: Role of non-radiative recombination and injection efficiency

With this paper we propose a detailed study of the gradual degradation of InGaN-based laser diodes and Light-Emitting Diodes submitted to electro-thermal stress. The two device structures have been processed from the same epitaxial wafer. Our purpose is to compare the behavior of the two devices by means of electro-optical measurements, electroluminescence characterization, and near field emission measurements. We demonstrate that: (i) stress induces a decrease in the optical power and an increase in threshold current; (ii) the two failure modes are strictly linked each other, and correlated to the increase in defect-related current components, indicating a substantial increase in defect density during degradation; (iii) analysis of characteristic temperature and near-field emission measurements do not indicate any strong variation of injection efficiency nor current confinement of the devices.