Effect of V-Shaped pits on optical properties of GaN-Based green light-emitting diodes

Abstract The optical properties of GaN-based green light-emitting diodes (LED) are investigated by transmission electron microscopy (TEM) and temperature-dependent micro-photoluminescence (μ-TDPL) in this study. Compared with the emission of normal c-plane multiple quantum wells (C-MQWs), the emission of C-MQWs close to V-shaped pits (V-pits) exhibits a shoulder peak phenomenon at cryogenic temperature, and the shoulder peak gradually disappears as the temperature increases. At room temperature, the peak of C-MQWs close to V-pits (C2) exhibits a red-shift. The formation of V-pits would induce strain relaxation. Strain relaxation can result in Indium (In) incorporation and localization, and reduced quantum-confined stark effects (QCSE). In incorporation and localization can lead to the red-shift of C2, reduced QCSE can cause the blue-shift of C2. Therefore, the red-shift of C2 arises from further In incorporation and localization of C-MQWs. It is worth noting that In incorporation and localization is dominant in the formation of V-pits for green InGaN/GaN C-MQWs. Additionally, the carriers limited in sidewall MQWs (S-MQWs) of V-pits escape into C-MQWs close to V-pits can mitigate the common phenomenon in which the emission intensity of C-MQWs decreases as the temperature increases, which helps improve the emission intensity of GaN-based green LEDs.