  Trench defects in multi-quantum wells (MQWs) have been considered as flawed
structures that severely degrade the internal quantum efficiency of
light-emitting diodes (LEDs) in the past. In this research, trench defects are
innovatively modulated into the structure to enhance the efficiency of red
InGaN LEDs. Specifically, dual-color MQWs structures are grown with green MQWs
at the bottom and red MQWs at the top. When high-density trench defects are
introduced into the green MQWs, the upper red MQWs exhibit a significant
wavelength redshift of 68 nm and approximately 6-fold luminescence enhancement
compared to those without trench defects. The wavelength redshift is attributed
to the increased indium incorporation due to the strain relaxation effect of
trench defects. Moreover, the luminescence enhancement originates from the
strong emission of the red MQWs inside trench defects. The mechanisms behind
the superior luminescent properties of red MQWs within trench defects are
explored in detail. Red InGaN LEDs with an internal quantum efficiency of 16.4%
are achieved by modulating the trench defects. The method of achieving
InGaN-based red emission by introducing trench defects is simple and
reproducible, requiring no additional substrate designs. This research provides
a novel pathway toward achieving high-efficiency red InGaN LEDs.
