Degradation-induced low frequency noise and deep traps in GaN/InGaN near-UV LEDs

Electrical stressing of near-UV (peak wavelength 390–395 nm) multi-quantum-well GaN/InGaN light emitting diodes at a high drive current of 650 mA and elevated temperature of 110 °C causes a significant degradation in external quantum efficiency (EQE), correlated with the formation of nitrogen interstitial-related electron traps at Ec − 0.8 eV. The dependence of the spectral density of current noise SI on forward current If showed two regions prior to accelerated aging, with SI ∼ If due to the current flow via localized leakage channels (presumably dislocations) and SI ∼ If2 related to the generation-recombination noise caused by the Ec − 0.8 eV states and Ev + 0.75 eV hole traps in the space charge region. Electrical stress for <922 h did not change the EQE but gradually increased both reverse and forward leakage current. This was accompanied by a gradual increase in the density of the hole traps, but not the electron traps. The mechanism appears to be the displacement of Ga and In atoms, with the interst...