Investigation of degradation dynamics of 265 nm LEDs assisted by EL measurements and numerical simulations

We studied four AlGaN-based 265 nm LEDs with increasing QW thickness (1.4, 3, 6 and 9 nm) during a constant current stress at 100 A cm-2. We focused our attention on the parasitic components of the emission spectra at low current levels and on the optical power recovery observed at high current levels. We associated every parasitic peak or band to a region in the device where they can be generated, also demonstrating if they are related to band-to-band emission or radiative emission through defects. At high current levels, we showed the simultaneous effect of the decrease in injection efficiency in the active region and the increase in non-radiative recombination, by fitting the EQE curves with a mathematical model. Moreover, we associated the optical power recovery with a generation of negative charge near the active region, which led to an increase in injection efficiency in the QW.