Wafer-Scale Growth and Transfer of Group III-Nitrides by Nanocrystalline Graphene for Flexible and 3D Stacking Devices

Devices with physical flexibility and 3D wafer-level packaging have attracted a great deal of interest for use in flexible and 3D stacking electronics, optics and photonic devices. Single-crystal group III-nitride thin films and nanorods are one of the most important semiconductors due to their tunable and direct band gap, excellent chemical stability, tunable electrical structures, and great piezoelectrical characteristics for applications on light-emitting diode (LED), piezoelectric nanogenerators, nanolasers, photosensors, photovoltaic cells, and hydrogen generation. High-quality crystalline III-nitrides thin films and nanorods are typically grown at high temperatures on rigid single crystalline substrates, such as Si (111), sapphire, and SiC, but these substrates cannot be adapted for flexible devices and 3DIC applications. In this work, we demonstrated a novel method for wafer-scale growing and transferring single crystalline GaN nanorods using nanocrystalline graphene. The achievements of wafer-scale growth of high density of GaN nanorods on the surface of the nanocrystalline graphene with the morphology of vertically oriented nanosheets, transferring the large-scale GaN nanorods to functional substrates, and fabricating the flexible nanogenerators for high performance have been proved to be an effective approach for flexible device, micro LED, and 3DIC fabrications. Moreover, our recent study showed that the morphology of the wafer-scale nanocrystalline graphene can be tuned to ultra flat thin film, which could be important for industrial applications for growth and transfer III-nitride thin films and nanorods. The results of these studies will have a considerable impact on the development of the flexible and 3D stacking devices and create new direction for fundamental study and their novel device applications.