Tsinghua Joint Condensed Matter Laboratory Improves the Performance of Red Light Micro LED Microdisplay

According to news on December 21, Tsinghua University and Beijing National Laboratory of Condensed Matter Physics, China, announced that the research team has improved efficiency and array uniformity of red light gallium nitride (InGaN) by using freestanding gallium nitride substrates (FGS). The researchers claim that this is the first InGaN red Micro LED with an etching-defined mesa size smaller than 5 μm.



The paper points out that the advantages of InGaN compared with the traditional red LED material AlInGaP include easier integration with green and blue InGaN LEDs, and better reduction of Micro LED device size due to less carrier migration of InGaN materials to sidewall defects

Although it is difficult for previous InGaN materials to achieve high-efficiency light emitting of red Micro LEDs, in recent years, under the efforts of the LED industry, InGaN materials red Micro LEDs have gradually been applied in micro displays, such as head-up displays (HUD) in the helmets of military aircraft pilots, and for AR/VR glasses equipment, etc.

However, the ultra-small size InGaN red Micro LED is still difficult to meet the light wavelength and efficiency required for small size and high current density micro-display products.


In response to the performance issues of InGaN red Micro LEDs, the research team demonstrated that the InGaN red Micro LED with a size of 1-20 μm was created based on an independent GaN substrate, and the amount of indium incorporated was increased compared with the Micro LED grown on the traditional sapphire substrate.
Experimental results show that at a size of 1μm, the InGaN red light Micro LED achieves an external quantum efficiency of 0.86% (on the wafer) and a wavelength of 613.6nm at a current density of 50A/cm².

In addition, the emission uniformity of 1μm Micro LED arrays grown on GaN substrates is significantly better than those grown on sapphire substrates. The research team stated that these results show that independent GaN substrates are beneficial to improving the performance of red InGaN Micro LEDs. (Compiled by LEDinside Irving)