Boosting External Quantum Efficiency and Thermal Stability of AlGaInP Red Mini-Light-Emitting Diodes for Active-Matrix Backlight Displays

High-efficiency AlGaInP-based miniatured light-emitting diodes (mini-LEDs) as red emitters are critical for realizing high-performance RGB mini-LED backlighting. However, as device dimensions shrink, the external quantum efficiency (EQE) of AlGaInP-based red mini-LEDs suffers from severe degradation due to sidewall damage induced by plasma etching. Moreover, in high-brightness display applications, the increased power density gives rise to elevated junction temperature and color shift, compromising the display effect. Here, we demonstrate high-efficiency AlGaInP-based red mini-LEDs with excellent thermal stability achieved through nitric acid (HNO 3 ) treatment. By effectively eliminating plasma-induced sidewall damage and surface oxides, the HNO 3 treatment extends the nonradiative recombination lifetime of carriers and thus mitigates sidewall nonradiative recombination. What is more, selective etching of AlInP layers forms a step-like sidewall morphology, which enhances light extraction through the sidewalls. Consequently, the EQE of AlGaInP-based red mini-LED treated with HNO 3 for 10 s is increased by 18.2% at 5 mA, compared to the untreated mini-LED. Due to the suppression of sidewall nonradiative recombination, the red mini-LEDs treated with HNO 3 exhibit a more uniform light emission distribution and a lower junction temperature than the untreated mini-LEDs at the same injection current. Furthermore, the red mini-LEDs treated with HNO 3 demonstrate high thermal stability and relatively small color shift under elevated temperatures. Additionally, these engineered red mini-LEDs were integrated into printed circuit boards using the chip-on-board technique, realizing an active-matrix mini-LED display with a resolution of 1080 × 960.