Evidence of optically induced degradation in gallium nitride optoelectronic devices

Abstract

We provide experimental evidence that gallium-nitride-based optoelectronic devices can be affected by a photon-driven degradation mechanism unrelated to catastrophic optical damage. Any role of current in such degradation is excluded by stress tests under laser irradiation in the open-circuit configuration; any role of temperature is ruled out by additional thermal tests, showing a different degradation mode. Given the high bond strength of GaN, lattice-damage-related degradation is unlikely. A possible cause, supported by the PL spectra, is the dehydrogenation of gallium vacancies, which causes an increase in the number of optically active defects and requires a removal energy lower than the photon energy.