Generation of defects and thermal recovery of blue InGaN-based LEDs after proton irradiation

We have submitted two different commercial blue InGaN-based LEDs to 3 MeV proton irradiation. The subsequent analysis was carried on by means of electrical, optical and capacitive characterization, in order to investigate the changes induced by the irradiation and the recovery after annealing time at high temperature (150 °C). Compared to the untreated device, we have found: (i) a variation of the current in forward- bias condition; (ii) a drop of the output optical power at higher fluences, uniform over the whole surface; (iii) a variation of the junction charge, well correlated with thechange of the diode ideality factor. These data suggest the creation of non-radiative recombination centers in the active region of the device. This hypothesis is confirmed by the results of the recovery tests: the increase of the optical power and its correlation with the recovery of the forward current is consistent with the annealing of those defects.