van der Waals integration of GaN light-emitting diode arrays on foreign graphene films using semiconductor/graphene heterostructures

We report the van der Waals integration of micropatterned GaN light-emitting diodes (LEDs) onto foreign graphene films. GaN micro-LEDs were selectively grown on a graphene substrate using a patterned SiO 2 mask, and then the whole device structure was laterally fixed by a polyimide insulator to form a united layer. After device fabrication, the LED/graphene heterostructure device was piled on the foreign graphene layers using a typical wet transfer technique of 2D crystals where the bottom graphene layer of the heterostructure was adhered to the foreign graphene only by van der Waals interactions. The transferred micro-LEDs showed well-aligned crystallographic orientations as well as reliable device performances, including strong light emissions, good rectifying behaviors of the current density–voltage curve, and good simultaneity between the electroluminescence intensity and the applied currents, ensuring reliable electrical connections and mechanical adhesions of the light-emitting layer to the foreign graphene films. Furthermore, the reliable adhesiveness allowed us to achieve device wearability, while the LEDs exhibited homogeneous light emissions under various bending conditions because of negligible external stress in the discrete micro-LEDs. Stickable light-emitting diodes (LEDs) were fabricated by selectively growing GaN micro-LEDs on a graphene sheet. Using the van der Waals interaction of the bottom graphene layer, the micro-LED/graphene heterostructures uniformly adhered to foreign graphene films. The transferred LEDs were fully operational and maintained good mechanical adhesion and electrical connections to the foreign graphene films under various bending conditions. Since the van der Waals integration method provides simple assembly processes of heterogeneous materials with negligible material compatibility issues, the LED/graphene heterostructure will be capable of integrating with various 2D devices.