Investigation of Photon-Generated Leakage Current for High-Performance Active Matrix Micro-LED Displays

In this paper, we investigated leakage current generated by light emission of micro-light emitting diode (LED) pixels in active matrix (AM) micro-LED displays. Custom-designed structures of metal cover with different coverage lengths were designed and fabricated to completely eliminate the photon-generated leakage current, thus enhancing the performance of AM driving circuits. Working principle of two transistors and one capacitor AM pixel and requirement of its driving transistors were also systematically discussed for liquid crystal displays, organic LED displays, and LED microdisplays. Transistors with the optimized metal-cover design have an ON/OFF-current ratio of 108, which is two orders of magnitude higher than those without metal cover. This concept was successfully implemented in a high-resolution and fine-pitch AM micro-LED display with a resolution of $400\times 240$ and a pixel pitch of $30~\mu \text{m}$ . Vivid images and movies were presented to show the great potential for wearable applications.