CAS Scientists Examine Size Effect of Micro-LEDs on Silicon Substrates

Due to their excellent efficiency, micro-LEDs have been employed in a variety of applications, including micro-displays, visible light communication, optical biochips, wearable devices, and biosensors. Achieving high pixel density and high resolution is one of the key challenges of working with micro-LED array displays. This is because it requires smaller and smaller chip sizes and pixel pitches.

A research team lead by Professor Jingqiu Liang from the Chinese Academy of Sciences’ Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) evaluated the size effect of aluminum gallium indium phosphide (AlGaInP) red Micro-LEDs on silicon substrates in a study recently reported in Results in Physics.

To prevent the light absorption characteristics of GaAs substrates, the scientists used a low-damage etching method and silicon substrates with greater heat dissipation.

Smaller micro-LEDs have a lower leakage current and a greater series resistance, allowing them to sustain higher current densities without the current crowding phenomenon.

Non-radiative recombination rises when the perimeter-to-area ratio of small-sized micro-LEDs grows, resulting in a reduced external quantum efficiency. Smaller micro-LEDs, on the other hand, can resolve the issue of high-current efficiency droop.

Furthermore, smaller micro-LEDs (80 m) have a reduced center wavelength shift due to greater heat dissipation under a high injection current.

It is important to note that for varied chip sizes, the determined local minimum suitable factor is constant. This suggests that sidewall treatment can reduce the size effect produced by process technology.

Since the present spread length of the smaller micro-LED chip is comparatively large, leading to higher current density at the border, the edge of the smaller micro-LED chip is brighter under the state of constant current density.

The size effect generated by the technique can be suppressed using AlGaInP red micro-LEDs manufactured on silicon substrate with a low damage etching formula. These findings provide a solid foundation for the design and fabrication of red micro-LEDs of various pixel sizes.

Journal Reference:

Fan, K., et al. (2022) Size effects of AlGaInP red vertical micro-LEDs on silicon substrate. Results in Physics. doi.org/10.1016/j.rinp.2022.105449.