Transfer Printed, Vertical GaN-on-Silicon Micro-LED Arrays with Individually Addressable Cathodes

Microscale light-emitting diodes (Micro-LEDs) have attracted intensive research attention due to their potential applications in high-resolution displays, wearables, and VR/AR headsets. However, their device performance can be compromised by the common Micro-LED lateral structure, usually with both two electrodes facing toward the p-side. Here, we developed printable, silicon-based vertical Micro-LEDs with two electrodes facing oppositely, which showed better heat dissipation, and were 60% brighter over conventional lateral Micro-LEDs. We further developed a novel double-tape-assisted transfer process, which allowed these vertical Micro-LEDs to be transferred completely to a polyimide tape in a simple yet reliable manner. Combined with a bonding scheme based on low-melting-point-patterned indium alloys, these printed Micro-LEDs on the tape can be further integrated onto silicon backplanes with a shared p-contact. Followed by forming an individual n-electrode connected to each pixel, a novel-inverted, vertical microdisplay prototype device with individually addressing cathodes was demonstrated for the first time.