Efficiency-droop reduction in blue InGaN light-emitting diodes with low temperature p-type insertion layer

• LT-pGaN/SL is inserted to alleviate the polarization field in the active region.
• Crystalline quality of epitaxial wafer is improved when LT-pGaN/SL is adopted.
• Experiment results show that the peak wavelength is more stable when LT-pGaN/SL is adopted.
• Our results show that photoelectric characteristic is improved when LT-pGaN/SL is adopted.
• Our results reveal that polarization field and hole injection efficiency are the main reasons for efficiency droop.

GaN based light emitting diodes with specially designed low temperature (LT) transition layers are investigated. Theoretical simulation shows that the LT-pGaN with LT-InGaN/GaN superlattice composite transition layer structure can effectively alleviate polarization field in the active layer and p-n junction region, consequently enhancing hole injection efficiency and electron blocking capability. Furthermore, the experimental results demonstrate that the low temperature (LT) transition layers can protect the active region from detrimental thermal annealing effect during high temperature p-GaN growth process. Finally, the reduced forward voltage and the enhanced output power about 42.2% were achieved at the injection current of 200 mA.