Interfacial engineering of graphene/GaN heterojunctions: h-BN intercalation and GaN doping

Abstract Understanding the influence and regulation mechanism of GaN substrate doping and hexagonal boron nitride (h-BN) layer thickness on the interfacial and electrical properties of single-layer graphene (SLG)/GaN heterojunctions is crucial for enhancing photoelectric performance of heterojunction devices. Here, we report the influence and regulation mechanism of the thickness of the h-BN insertion layer (1–5 layers) and the doping type of GaN (n- or p-type) on the electrical and interfacial physical properties of heterojunctions, including charge transfer, barrier height, and built-in potential. Our research shows that h-BN enhances barrier heights by suppressing charge transfer. Compared with the SLG/h-BN/n-GaN heterojunction with a larger depletion region area, the SLG/h-BN/p-GaN heterojunction with a smaller depletion region area has a stronger built-in electric field intensity. As h-BN thickness increases, the Fermi level of the SLG on both n-GaN and p-GaN substrates exhibits a gradual trend toward approaching the Dirac point. Furthermore, our calculations further reveal that the contact potential difference of the SLG/h-BN/n-GaN junction increases with h-BN thickness, while showing an opposite decreasing trend for the SLG/h-BN/p-GaN junction. Quantitative analysis of the interface trap charge density indicates that the surface characteristics of GaN can significantly influence the charge transport and interfacial physical properties at the heterojunction interface. These results will benefit recent topical application research on regulation strategies for 2D/3D heterojunction interfaces.