  We report the growth of high-quality GaN epitaxial thin films on
graphene-coated c-sapphire substrates using pulsed-mode metalorganic
vapor-phase epitaxy, together with the fabrication of freestanding GaN films by
simple mechanical exfoliation for transferable light-emitting diodes (LEDs).
High-quality GaN films grown on the graphene-coated sapphire substrates were
easily lifted off using thermal release tape and transferred onto foreign
substrates. Furthermore, we revealed that the pulsed operation of ammonia flow
during GaN growth was a critical factor for the fabrication of high-quality
freestanding GaN films. These films, exhibiting excellent single crystallinity,
were utilized to fabricate transferable GaN LEDs by heteroepitaxially growing
InxGa1-xN/GaN multiple quantum wells and a p-GaN layer on the GaN films,
showing their potential application in advanced optoelectronic devices.
