Degradation of InGaN-based LEDs: Demonstration of a recombination-dependent defect-generation process

This paper provides insights into the degradation of InGaN-based LEDs by presenting a comprehensive analysis carried out on devices having two quantum wells (QWs) with different emission wavelengths (495nm and 405nm). Two different configurations are considered: one with the 495nm QW closer to the p-side and one with the 495nm QW closer to the n-side. The original results collected within this work indicate that (i) during stress, the devices show an increase in defect-related leakage both in reverse and low-forward voltage ranges: current increases with the square-root of stress time, indicating the presence of a diffusion process; (ii) stress induces a decrease in the luminescence signal emitted by both quantum wells: the drop in luminescence is stronger when measurements are carried out at low current levels, indicating that degradation is due to the generation of Shockley-Read-Hall recombination centers; (iii) remarkably, the degradation rate is linearly dependent on the luminescence signal emitted before stress by the well, indicating that carrier density impacts on degradation; and (iv) the optical degradation rate has a linear dependence on the stress current density. The results strongly suggest the existence of a recombination-driven degradation process: the possible role of Shockley-Read-Hall and Auger recombination is discussed. The properties of the defects involved in the degradation process are described through steady-state photocapacitance measurements.