Photocurrent spectroscopy evidence for stress-induced recombination centres in quantum wells of InGaN/GaN-based light-emitting diodes

The microscopic phenomena leading to degradation of blue LEDs under forward current stress have been investigated by means of photocurrent (PC) spectroscopy. A versatile model, developed for the simulation of PC spectra, allowed us to separate the photocurrent signal by carriers generated inside the InGaN quantum wells (QWs) from the signal by carriers generated in the bulk GaN. The comparison of simulation and experiment showed that the QW component of photocurrent is the only one to decrease. This strongly supports the hypothesis that degradation is mostly induced by the localized introduction of non-radiative centres in the QW region