Wafer-Level Monolithic Integration of Vertical Micro-LEDs on Glass

In an earlier study micro-LED micro display (<1 inch) on silicon CMOS backplane was demonstrated for augmented reality (AR) applications. Here we report the feasibility of wafer-level monolithic integration of micro-LEDs on glass substrate/backplane. Such issues as the cracking of GaN epitaxial layer, the deviation of alignment, and the peeling of insulator are discussed. SU-8 is proposed as the insulator material in vertical micro-LEDs, resulting into improved light extraction efficiency and allowing for the reduced light crosstalk between sub pixels if the integrated reflective mirrors are used. A directly driven micro-LED parallel array with a resolution of 320 x 720 with individual LED size ranging from 5 mu m to 28 mu m is demonstrated. It is believed that this monolithic technology on glass will play an important role in future high performance and low cost wearable and/or phone displays.