Mass transfer and heterogeneous integration of thin-film III-nitride micro-LEDs via metal-metal bonding

To overcome the challenges faced by conventional laser lift-off and transfer methods for light-emitting III-nitride material systems, such as high processing costs and compatibility issues with long-wavelength devices, this study demonstrates centimeter-scale mass transfer of thin-film micro-LEDs using electrochemical (EC) etching and metal-metal bonding for heterogeneous integration. III-nitride micro-LED structures incorporating a sacrificial layer were epitaxially grown by metal–organic chemical vapor deposition (MOCVD). Following the fabrication of centimeter-scale micro-LED arrays with lateral device sizes ranging from 100 µm to 3 µm on the growth substrate, EC etching of the sacrificial layer and Au–Au flip-chip bonding were employed to mass transfer the submicron-thin devices onto Si substrates. The structural, optical, and electrical properties of the transferred devices were characterized using scanning electron microscopy, atomic force microscopy, cathodoluminescence, and electroluminescence, demonstrating preservation of material quality and device performance before and after transfer.