Regulating the contact properties of single-layer graphene/GaN heterojunctions via h-BN intercalation

Understanding the influence and regulation mechanism of the thickness of hexagonal boron nitride (h-BN) layers on the interfacial physical properties of single-layer graphene (SLG)/GaN heterojunctions is crucial for adjusting the interfacial band structure of the heterojunctions and enhancing their photoelectric performance. Here, we investigated the influence and regulation mechanism of few-layer h-BN (zero to five layers) on the interfacial physical properties (such as built-in potential, depletion region, barrier height, etc.) of SLG/GaN heterojunctions. The contact properties of SLG/h-BN/GaN heterojunctions were nondestructively characterized using Kelvin probe force microscopy (KPFM). The KPFM measurement results show that the potential of SLG on the GaN surface varies with the increase in the number of h-BN layers. Research shows that the h-BN insertion layer can regulate (increase or decrease) 13 interfacial physical properties of the SLG/GaN heterojunction. The critical insertion layer of h-BN (two layers) is identified, beyond which the blocking effect on charge transfer diminishes with increasing layer number. Furthermore, the theoretical calculations show that the built-in potential of GaN and the Fermi level shift of graphene are the key parameters determining the interfacial physical properties of the heterojunction. The density of states existing on the GaN surface can significantly affect the interfacial charge transfer. These results will benefit recent topical application research on the interface control strategy of graphene/GaN heterojunctions by using two-dimensional insulating materials.