Uni-axial external stress effect on green InGaN/GaN multi-quantum-well light-emitting diodes

Abstract

The influence of uni-axial external stress on green InGaN/GaN multi-quantum-well (MQW) light-emitting diodes (LEDs) is evaluated. LEDs with external tensile stress show an improvement in light output power up to 35% at an injection current of 20 mA. The maximum output power can be obtained by considering the residual mechanical stress induced by the wafer bowing. In contrast, when the LEDs were exposed to an external compressive stress, the light output power was reduced by ∼7% at an injection current of 20 mA. Moreover, when the compressive strain developed in InGaN/GaN MQW active region is relaxed, the peak wavelength of electroluminescence was blue-shifted. The results confirmed that applying external tensile stress effectively compensates for the compressive strain and alters the piezoelectric field in the InGaN/GaN active region, and hence increases the probability of radiative recombination.