Active Matrix Monolithic LED Micro-Display Using GaN-on-Si Epilayers

An active matrix light emitting diode (LED) microdisplay system was demonstrated with GaN-on-Si epilayers and a custom-designed CMOS backplane using an Au-free Cu/Snbased metal bonding method. The blue micro-LED array consists of 64 × 36 pixels with a pitch size of 40 μm × 40 μm and a pixel density of 635 pixels/in (ppi). The Si substrate for the LED growth was removed by reactive ion etching (RIE) using SF6based gas after flip-chip bonding. Crack-free and smooth GaN layers in the display area were exposed. Images and videos with 4-bit grayscale could be clearly rendered, and light crosstalk was significantly suppressed compared to its counterpart using the GaN-on-sapphire epilayers. The demonstration suggests the tremendous potential of the low-cost and large-scale GaN-on-Si epilayers and cost-effective Au-free Cu/Sn-based bonding scheme for micro-display applications.