Epitaxy of Single-Crystalline GaN Film on CMOS-Compatible Si(100) Substrate Buffered by Graphene

Fabricating single-crystalline gallium nitride (GaN)-based devices on a Si(100) substrate, which is compatible with the mainstream complementary metal-oxide-semiconductor circuits, is a prerequisite for next-generation high-performance electronics and optoelectronics. However, the direct epitaxy of single-crystalline GaN on a Si(100) substrate remains challenging due to the asymmetric surface domains of Si(100), which can lead to polycrystalline GaN with a two-domain structure. Here, by utilizing single-crystalline graphene as a buffer layer, the epitaxy of a single-crystalline GaN film on a Si(100) substrate is demonstrated. The in situ treatment of graphene with NH₃ can generate sp³ CN bonds, which then triggers the nucleation of nitrides. The one-atom-thick single-crystalline graphene provides an in-plane driving force to align all GaN domains to form a single crystal. The nucleation mechanisms and domain evolutions are further clarified by surface science exploration and first-principle calculations. This work lays the foundation for the integration of GaN-based devices into Si-based integrated circuits and also broadens the choice for the epitaxy of nitrides on unconventional amorphous or flexible substrates.