Red emitting InGaN based micro-LEDs for micro-display – REIDI

Micro-displays for augmented and virtual reality (AR/VR) now generates strong interests. To get a red-green-blue (RGB) full color micro-display with a pixel pitch below 10 µm, needed for AR/VR, the use of the same material family in a monolithic way should provide the best approach. The InxGa1-xN alloy appears thus as the best candidate. However, the external quantum efficiency of III-nitride light emitting diodes (LEDs) dramatically drops for a wavelength emission above 500 nm, which constitutes a technical challenge for the red emission with InGaN. This limitation is explained by the strong material degradation of the InGaN alloy for high In content (xIn > 25%). To enhance the In incorporation rate while maintaining a high crystalline quality, the main solution consists in reducing the strain in the quantum well region by using a high quality relaxed InGaN pseudo-substrate with the ad-hoc in-plane lattice parameter. However, such a pseudo-substrate does not exist yet. In the REIDI project, three innovative substrate solutions aiming at fabricating the adequate relaxed InGaN pseudo-substrate will be addressed. A full InGaN LED structure will be adapted and overgrown in order to realize finally highly efficient InGaN based red micro-LEDs. This project represents an essential step towards the future manufacture of monolithic full color micro-display.