Emission efficiency enhanced by introduction of the homogeneous localization states in InGaN/GaN multiple quantum well LEDs

• Properly decreasing the growth temperature of InGaN QWs benefits for improving the emission efficiency of InGaN/GaN MQWs.
• Localization states in InGaN QWs changes with the decrease of growth temperature of InGaN QWs.
• The formation of large In-rich regions with defects may be suppressed when the growth temperature of QWs decreases.

A series of InGaN/GaN multi-quantum well (MQW) LEDs are grown by using metalorganic chemical vapor deposition (MOCVD) with similar structure but at different temperature, their structural and optical characteristics are investigated in detail. It is unexpectedly found that the output power of LEDs increases markedly when the growth temperature of InGaN QWs decreases from 820 °C to as low as 770 °C. This is attributed to the variation of localization states with the decrease of growth temperature. In the lower temperature (LT) grown InGaN/GaN MQWs, the formation of large and high indium content In-rich regions accompanied with defects is better suppressed, while the formation of shallower and more homogeneous localization states, behaving as effective luminescence centers, are more favored. Therefore, enhanced emission intensity is observed in the LT-grown InGaN/GaN MQW LEDs.