Origin of efficiency droop in GaN-based light-emitting diodes

TLDR

The study investigates the cause of efficiency droop in GaInN/GaN multiple‑quantum‑well LEDs. Measurements and simulations reveal that droop originates from carrier escape driven by polarization fields, not from junction temperature or MQW efficiency, and that using quaternary AlGaInN compositions reduces these polarization effects, thereby mitigating droop and improving efficiency.

Abstract

The efficiency droop in GaInN∕GaN multiple-quantum well (MQW) light-emitting diodes is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the photoluminescence output as a function of excitation power shows no droop, indicating that the droop is not related to MQW efficiency but rather to the recombination of carriers outside the MQW region. Simulations show that polarization fields in the MQW and electron blocking layer enable the escape of electrons from the MQW region and thus are the physical origin of the droop. It is shown that through the use of proper quaternary AlGaInN compositions, polarization effects are reduced, thereby minimizing droop and improving efficiency.