Influence of p-GaN annealing on the optical and electrical properties of InGaN/GaN MQW LEDs

Optical and electrical properties of InGaN/GaN multiple quantum wells (MQWs) light emitting diodes (LEDs) annealed in pure O-2 ambient (500 degrees C) and pure N-2 ambient (800 degrees C) were systematically investigated. The temperature-dependent photoluminescence measurements showed that high-temperature thermal annealing in N-2 ambient 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 N-2 ambient was lower than that annealed in O-2 ambient at room temperature. Electrical measurements demonstrated that the LEDs annealed in O-2 ambient were featured by a lower forward voltage and there was an increase of similar to 41% in wall-plug efficiency at 20 mA in comparison with the LEDs annealed in N-2 ambient. It is thus concluded that activation of the Mg-doped p-GaN layer should be carried out at a low-temperature O-2 ambient so as to obtain LEDs with better performance. (C) 2014 Elsevier B.V. All rights reserved.