Strategies for improving light extraction in thin film-based InGaN micro-LED arrays for AR displays

The LED thin film technology enables light outcoupling via the n-side after removal of the epitaxial growth substrate. Therefore, this technology allows compact integration of micro-LED arrays with single emitters as small as one micrometer and CMOS driving circuits on a silicon wafer, building a promising platform for highresolution AR displays. Despite the potential impact of thin film-based micro-LED arrays on practical AR applications, this technology and the challenges involved are still relatively unexplored. We present fundamental optical properties of thin film-based micro-LED arrays with different pixel sizes down to 1 µm, and we reveal the role of wave optical effects inside micro-LEDs. To address remaining challenges in light outcoupling, we explore different strategies in the micro-LED chip design for improving light extraction efficiency and directionality.