Sidewall defects

Finland based Comptek Solutions announced that it has successfully closed its its Series A funding round, raising a total of 8 million Euro, from the Horizon Europe EIC Fund, LIFTT (Italian venture firm) and an undisclosed key strategic partner.

The funds will be used to accelerate Comptek's technology implementation, and scale up its growth. Comptek was founded in 2017, and develops passivation technology for Optoelectronics and power applications.

Researchers from Korea's KAIST have found that by changing the epitaxial structure of microLEDs, it is possible to fundamentally resolve the problem of efficiency degradation in microLED devices. In other words, it is possible to create microLEDs in which the efficiency does not drop with size. 

The researchers discovered that the specific epitaxial structure of the microLED changes how the current drives to the sidewall of the microLEDs. Based on that, the researchers developed a epitaxial structure that is not sensitive to sidewall defects. The proposed structure also reduces generated heat by about 40% compared to standard microLEDs.

China-based MicroLED microdisplay developer Jade Bird Display announced that it is developing a native full-color microLED microdisplay. JBD is working to integrate InGaN and AlInGaP on the same chip, fabricated using conventional thin-film processes.

JBD says it developed a proprietary (and patented) technology in which the epitaxy layers were designed to be less susceptibility to edge effects, which helps to increase the display's efficiency. JBD's technology also enables effective mesa sidewall passivation. JBD refers to its technology as monolithic hybrid integration and says it can reach a PPI of up to 10,000 with a pixel pitch of 2.5 um.

Researchers from King Abdullah's University of Science & Technology (KAUST) in Saudi Arabia developed GaN and InGan red microLED devices that are highly efficient.

The researchers managed to increase the efficiency of their previous design by a new chemical treatment that removes damages at the microLED sidewalls (created during the fabrication process) and also retains the high crystal quality at the InGaN and GaN sidewall interfaces.

This article is a first article in a short series of articles that discuss the efficiency of microLED displays. And we start with the quantum efficiency of microLED chips.

LED devices are quite efficient. In the chart above (by the DoE), you can see that the efficiency (external quantum efficiency, or EQE) of a blue LED is around 70%. It is generally accepted that as LED chip size decreases, the efficiency of LED devices decreases as well.