Pulsed-mode metalorganic vapor-phase epitaxy of GaN on graphene-coated c-sapphire for freestanding GaN thin films

TL;DR

This paper demonstrates a method for growing high-quality GaN films on graphene-coated sapphire, enabling easy transfer and application in flexible LEDs, with pulsed ammonia flow being crucial for film quality.

Contribution

Introduces a pulsed-mode MOCVD process for GaN growth on graphene-coated sapphire and a simple exfoliation technique for freestanding GaN films used in transferable LEDs.

Findings

High-quality GaN films can be transferred using thermal release tape.

Pulsed ammonia flow improves GaN film crystallinity.

Freestanding GaN LEDs show promising optoelectronic performance.

Abstract

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.