InGaN-based light-emitting diodes (LEDs) have been widely accepted as highly efficient light sources capable of replacing incandescent bulbs. However, applications of InGaN LEDs are limited to small devices because their fabrication process involves expensive epitaxial growth of InGaN by metalorganic vapor phase epitaxy on single-crystal wafers. If we can utilize a low-cost epitaxial growth process, such as sputtering on large-area substrates, we can fabricate large-area InGaN light-emitting displays. Here, we report the growth of GaN (0001) and InGaN (0001) films on amorphous SiO2 by pulsed sputtering deposition. We found that using multilayer graphene buffer layers allows the growth of highly c-axis-oriented GaN films even on amorphous substrates. We fabricated red, green, and blue InGaN LEDs and confirmed their successful operation. This successful fabrication of full-color InGaN LEDs on amorphous substrates by sputtering indicates that the technique is quite promising for future large-area light-emitting displays on amorphous substrates.

GaN films were grown on a multilayer graphene (MLG)/amorphous SiO2 stack by pulsed sputtering deposition and their structural properties were investigated. The GaN films on MLG show high c-axis orientation. In addition, the GaN films exhibit coexisting zincblende and wurtzite phases, but the zincblende phase is suppressed by the insertion of AlN interlayers. The polarity control of the GaN films was demonstrated using AlN interlayers with and without surface oxidation. These results indicate that the proposed technique can yield high-quality Ga-polarity GaN films on MLG for potential use in large-area GaN-based optical and electronic devices.

SUMMARYCrystalline GaN films can be grown even on amorphous substrates with the use of graphene buffer layers by pulsed sputtering deposition (PSD). The graphene buffer layers allowed us to grow highly c-axisoriented GaN films at low substrate temperatures. Full-color GaN-based LEDs can be fabricated on the GaN/graphene structures and they are operated successfully. This indicates that the present technique is promising for future large-area light-emitting displays on amorphous substrates.

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