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

摘要

Optical and electrical properties of InGaN/GaN multiple quantum wells (MQWs) light emitting diodes(LEDs) annealed in pure O_2 ambient (500 ℃) and pure N_2 ambient (800 ℃) were systematically investigated. The temperature-dependent photo luminescence 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 ~41 % in wall-plug efficiency at20 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.