Mar 6, 2014

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 Oambient (500 °C) and pure N2 ambient (800 °C) were systematically investigated. The temperature-dependent photoluminescence measurements showed that high-temperature thermal annealing in N2 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 much more dislocations out of the trap centers due to high-temperature annealing. As a result, the radiative efficiency of the sample annealed in N2 ambient was lower than that annealed in O2 ambient at room temperature. Electrical measurements demonstrated that the LEDs annealed in O2 ambient was featured by a lower forward voltage and an increase of 41% in wall-plug efficiency at 20 mA in comparison with those annealed in N2 ambient. It is thus concluded that activation of the Mg-doped p-GaN layer should be carried out at a low-temperature O2 ambient so as to obtain better performance of LEDs.
Highlights
• The GaN-based LEDs wafer were annealed in N2 ambient (800 °C)and O2 (500 °C) ambient.
• The N2 thermal annealing may induce more dislocations in InGaN/GaN MQWs.
• Mg can be further activated during thermal annealing in O2 ambient.
• The O2 thermal annealing shows better optical and electrical performance of LEDs.

Source:Physica E: Low-dimensional Systems and Nanostructures

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