In a World first, Soft-Epi and Sundiode have jointly developed a monolithic red, green and blue (RGB) stacked epi wafer for micro LED displays using only InGaN materials without wafer bonding. This is another big step for micro LED displays after the development of an InGaN based red LED last year.

South Korean-based Soft-Epi has a unique GaN epitaxy technology, with a focus on manufacturing InGaN epitaxial growth for visible light including nitride-based red LEDs. Sundiode is a US Silicon Valley based company that develops micro LED technology for display applications including augmented reality (AR) and mixed reality (MR) as well as heads-up displays (HUDs).

In order to realise a next-generation full- colour micro-LED display with ultra-high resolution (5000 PPI), it's necessary to go through a very complicated process of using wafer bonding technology and removing the substrate after individual epitaxial growth of R, G and B on each wafer. This process has been the biggest problem in implementing full- colour micro LED displays.

The two companies have realised the world's first RGB epitaxial layers with independent pn junctions on a single substrate with a single epitaxy growth without additional wafer bonding process. This new development has been made through Soft-Epi's epitaxial growth technology and Sundiode's design technology.

This is completely different from the previous conventional method, wafer bonding technology, or colour control method using wavelength shift according to current density change. It is a monolithic stacked RGB structure that can drive RGB colours independently. This is regarded as an ideal RGB pixel structure for manufacturing high-resolution micro-displays.

Ref: https://compoundsemiconductor.net/article/116074/Worldand_s_first_monolithic_InGaN_RGB_LED_for_%C2%B5LED_displays