Quantum Barrier Engineering Enables Carrier Redistribution for High-Efficiency Green InGaN Micro-LEDs at Reduced Operating Current Density

Achieving high efficiency in green InGaN microlight-emitting diodes (Micro-LEDs) at low current densities required for active-matrix microdisplays is fundamentally limited by inefficient hole transport and nonuniform carrier distribution in multiple quantum wells (MQWs). Here, we systematically investigate the influence of quantum barrier (QB) thickness and the number of MQW periods on the low-current performance of green Micro-LEDs. Increasing the QB thickness from 10 to 25 nm significantly improves the MQW interface quality and enhances the peak wall-plug efficiency (WPE) to 52.4% at an ultralow current density of 0.42 A·cm–2, corresponding to a peak external quantum efficiency of 48.1%. Carrier transport analysis reveals that thicker QBs suppress interwell hole transport, promote carrier localization within the radiatively active quantum wells near the p-side, and enhance electron–hole overlap, thereby reducing Shockley-Read-Hall (SRH) recombination and shifting the transition from SRH to radiative-dominated recombination from 5.71 to 1.87 A·cm–2. Furthermore, optimization of the MQW period number identifies a five-period active region that maximizes carrier utilization while maintaining sufficient effective recombination volume. These results establish a unified active-region design principle in which QB engineering controls the number of effectively radiative quantum wells, enabling MQWs to be optimized for high-efficiency III-nitride Micro-LEDs operating under display-relevant low-current conditions.