Direct van deer Waals epitaxy of multiband-emitting InGaN-based LEDs on graphene for phosphor-free white light illumination

The white light-emitting diodes (LEDs), a kind of representative multiband light emitters, which are generally manufactured by coating phosphor with InGaN-based blue LED chips, are widely used in illumination and display. However, the degradation and wavelength-conversion loss of phosphor are still issues which shorten the life of these LEDs. Herein, we demonstrate a convenient way to fabricate phosphor-free multiband-emitting LEDs without any external process or additional dielectric interlayers, utilizing only graphene as substrate for direct van deer Waals epitaxy (vdWE) of multiple-facet InGaN-based LEDs. Taking advantage of the low nucleation density of GaN on graphene, the surface morphology of the films was controlled as complete voids without flat. The morphology of InGaN/GaN multi quantum wells followed with the multiple-facet GaN, which caused the variation of indium concentration in different lattice plane of multi quantum well and led to multiband emission. Those findings reveal the roles of graphene in growth of III-nitride and provide valuable insights into the application of graphene for phosphor-free white light illumination.