Surface texturing boosts efficiency of red mini-LEDs
Researchers enhance efficiency of AlGaInP-based red mini-LEDs by surface texturing technology
Researchers from Wuhan University, University of Waterloo, and Jiangxi SMTC Semiconductor have reported a surface texturing technology to boost light extraction efficiency (LEE) of AlGaInP-based red vertical mini-LEDs.
“We utilise a wet chemical etching method to fabricate a porous n-AlGaInP surface on the AlGaInP-based red vertical mini-LEDs, which suppresses total internal reflection (TIR) at n-AlGaInP/air interface and enhances light scattering effect. As a result, compared with the red mini-LED with a smooth n-AlGaInP surface, the vertical mini-LEDs with the porous n-AlGaInP surface reveal improvement in light output power and external quantum efficiency (EQE).” said professor Shengjun Zhou, who led the team.
Owing to the advantages of small size, high luminance, high colour-rendering index and long lifetime, AlGaInP-based red mini-LEDs have been widely applied in high-resolution full-colour self-emissive displays and locally dimmable backlight units. Nevertheless, further improvements are demanded to boost the EQE of AlGaInP-based red mini-LEDs. Despite the fact that the internal quantum efficiency of AlGaInP-based red mini-LEDs can reach nearly 100 percent, the LEE is limited because of the severe TIR and Fresnel reflection at the semiconductor–air interface, resulting in low EQE of AlGaInP-based red mini-LEDs.
The researchers introduce a porous n-AlGaInP surface on AlGaInP-based red mini-LEDs by using a wet etching method to boost light extraction. The effects of etching time on the surface morphology of the porous n-AlGaInP surface are further investigated. The AlGaInP-based red mini-LED with the maximum density of the pores exhibits an increment of EQE up to 38.9 percent at 20 mA, as compared to AlGaInP-based red mini-LED with a smooth n-AlGaInP surface. With the potential to boost LEE, the surface texturing technology represents a significant contribution to the mass production of efficient AlGaInP-based red vertical mini-LEDs.
Reference
‘Improvement of light extraction efficiency in AlGaInP-based vertical miniaturised-light-emitting diodes via surface texturing’ by Siyuan Cui et al; Optics Letters 49(6): 1449 (2024) https://doi.org/10.1364/OL.519723
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