Study on AlN buffer layer for GaN on graphene/copper sheet grown by MBE at low growth temperature

Growth of III-nitrides on non-single-crystalline substrates at low growth temperature will greatly benefit the development of large-scale and flexible display/lighting technologies. Two-dimensional (2D) materials such as graphene and hexagonal boron nitride have the similar in-plane lattice arrangements to III-nitrides, hence III-nitrides can be grown on non-single-crystalline substrates by Van der Waals epitaxy through insertion of 2D material layers. In this paper, the growth of AlN buffer layer has been studied in order to obtain high-quality GaN film on graphene/copper sheet using molecular beam epitaxy at low growth temperature. The results reveal that the lateral coalescence of the AlN buffer layer is crucial in the initial stages of Van der Waals epitaxy. At low growth temperature, the migration enhanced epitaxy mode is an effect way to significantly enhance the lateral coalescence of AlN buffer layer on the surface of the graphene insertion layer. By adopting the AlN buffer layer as a template, unstrained GaN single-crystalline film is obtained on graphene/copper sheet at 530 degrees C. This result is believed to be applicable to Van der Waals epitaxy of III-nitride on other 2D material/non-single-crystalline substrates, which is a promising candidate for developing transferable and flexible devices. (C) 2019 Elsevier B.V. All rights reserved.