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

• Published in: Applied physics letters 2017-08, Vol.111 (6)
• Main Authors: Lee, In-Hwan, Polyakov, A. Y., Hwang, Sung-Min, Shmidt, N. M., Shabunina, E. I., Tal'nishnih, N. A., Smirnov, N. B., Shchemerov, I. V., Zinovyev, R. A., Tarelkin, S. A., Pearton, S. J.
• Format: Article
• Language: English
• Subjects: Applied physics; Degradation; Density; Dislocations; Electron traps; Gallium nitrides; High temperature; Hole traps; Indium gallium nitrides; Interstitials; Leakage current; Multi Quantum Wells; Noise; Organic light emitting diodes; Quantum efficiency; Space charge; Variation
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4985190

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 ∼ If 2 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, the peak EQE decreased from 26% to 15% and was accompanied by a further increase in the leakage current and density of both types of traps. One of the 20 studied diodes showed an anomalously high forward leakage current, and the noise spectrum in it was dominated by the SI ∼ If 4 region typical for the presence of local overheated areas (presumably local In composition fluctuations). The EQE of this sample began to degrade after a much shorter stress time of 258 h.