Effect of compressive strain relaxation in GaN blue light-emitting diodes with variation of n ⁺ -GaN thickness on its device performance

The effects of compressive strain relaxation with increasing n-GaN thickness on device performances of GaN blue light-emitting diodes (LEDs) were investigated. It was found that the compressive strain relaxation in LEDs with thicker n-GaN occurred more considerably, following by the growth of active layer and p-GaN, and generated many stacking faults right beneath the InGaN active layer, which might be related to a decrease of the LED output power. On the contrary, the LED photoluminescence intensity increased surprisingly with n-GaN thickness. It was understood that the compressive strain relaxation enhanced localized states in InGaN wells.