Monolithic RGB micro-LED arrays on silicon with directional emission pave the way to cost effective high brightness low power consumption micro-displays for augmented reality

The major challenges of micro-displays for augmented reality are to find ways of drastically increasing the amount of lumens provided to the user eyes via an optical system with a projector form factor as small as possible while keeping the power consumption as low as possible. Micro-LED micro-displays can potentially meet those requirements because the brightness of micro-LEDs can be several orders of magnitude higher than the competitive technologies such as OLED or LCOS, and with an excellent contrast ratio. However, most of the micro-LED technologies experience efficiency loss when reducing the size of the micro-LEDs, provide a lambertian emission, which limits the coupling efficiency with an optical waveguide and need complex processes such as junction stacking or color conversion for RGB array manufacturing. Those issues limit the capability of those micro-LED technologies to produce efficient and cost competitive RGB micro-displays. Aledia has developed a technology allowing to grow on 200mm or 300mm Si wafers GaN nanowires (NWs). Those NWs can be used for manufacturing LED structures and Aledia has developed a technology allowing to grow in the same growth run the Red, Green and Blue active regions of a RGB array with a subpixel pitch that can be reduced down to 1.25µm. In addition, the periodic arrangement of the NWs in the subpixels allow to obtain a photonic crystal effect that greatly increases the directivity of the emission of the subpixels. In this presentation we will present results showing our capability to obtain RGB LED arrays in a single growth run as well as our capability to control the directionality of the emission.