High quantum efficiency AlInP/GaInP multi-quantum well LED at ultra-low driving current for display application

Abstract

One of the technology bottlenecks for inorganic MicroLED display is the considerably low quantum efficiency of Red LED at low injection current density. Conventional Red LEDs, which are based on the AlGaInP/GaInP MQW structure have large surface recombination velocity, resulting in reduced quantum efficiency at low injection current density with a pixel size scaling. Since non-radiative Shockley Read Hall (SRH) recombination is the fundamental limiting mechanism of internal quantum efficiency (IQE) at low current density, modulation of carrier population in the quantum well (QW) by re-designing QW must be taken into account to increase IQE and decrease SRH recombination at low current density. Therefore, in this work, we propose and discuss the simulation of the new QW design using AlInP/GaInP QW system, which has a larger valance band offset and hole density in quantum wells, providing a remarkably higher IQE value at a wider current density range compared to conventional AlGaInP/GaInP QW structure. Finally, we fabricated newly designed Red LEDs and the fabricated devices also showed very high IQE at a lower current density range of $0.1~1 A/cm^{2}$, which is the record-high IQE at this current density range. With these results, we believe that this is the first step and important milestone to realize the high-efficiency pixel at low current density for display applications.