Optical and electrical properties of InGaN/GaN multiple quantum wells (MQWs) light emitting diodes (LEDs) annealed in pure O2ambient (500 C) and pure N2ambient (800 C) were systematically investigated. The temperature-dependent photoluminescence measurements showed that high-temperature thermal annealing in N2ambient can induce indium clusters in InGaN MQWs. Although the deep traps induced by indium clusters can act as localized centers for carriers, there are many more dislocations out of the trap centers due to high-temperature annealing. As a result, the radiative efficiency of the sample annealed in N2ambient was lower than that annealed in O2ambient at room temperature. Electrical measurements demonstrated that the LEDs annealed in O2ambient were featured by a lower forward voltage and there was an increase of ~41% in wall-plug efficiency at 20 mA in comparison with the LEDs annealed in N2ambient. It is thus concluded that activation of the Mg-doped p-GaN layer should be carried out at a low-temperature O2ambient so as to obtain LEDs with better performance. © 2014 Elsevier B.V.
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