Effect of Aging on the Photoelectrical Properties of AlGaInP LEDs

We report on the nonmonotonous variation of photoelectrical properties of commercial AlGaInP LEDs during the aging process. The light-generated current and short-circuit photocurrent were found to drop by the factors of 2 and 1.5, respectively, after about 3 h of aging at the rated forward current of 1400 mA with subsequent recovery and stabilization within $\sim 1000$ h of aging. The temporal minima of photocurrents were accompanied by increased photoconductivity revealed from the negative differential photovoltage under modulated photoexcitation as well as by the minimum of optical output and the maximum of the ideality factor of the LEDs at low forward currents. The observed temporal variation of the photoelectrical properties was attributed to the interplay of recombination-enhanced growth and annealing of defects responsible for nonradiative recombination and photoconductivity in the active and cladding layers of the LEDs, respectively.