Tunneling characteristics in chemical vapor deposited graphene – hexagonal boron nitride – graphene junctions

Large area chemical vapor deposited graphene and hexagonal boron nitride was used to fabricate graphene – hexagonal boron nitride – graphene symmetric field effect transistors. Gate control of the tunneling characteristics is observed similar to previously reported results for exfoliated graphene – hexagonal boron nitride – graphene devices. Density-of-states features are observed in the tunneling characteristics of the devices, although without large resonant peaks that would arise from lateral momentum conservation. The lack of distinct resonant behavior is attributed to disorder in the devices, and a possible source of the disorder is discussed. Graphene is considered a promising candidate for future electronic devices owing to the high mobility of its carriers, linear dispersion, and perfect two-dimensional (2D) confinement. However, monolayer graphene-based transistors have a low switching ratio owing to the semimetallic nature of graphene. Graphene-insulator-graphene symmetric field effect transistors (SymFET), where a bottom gate controls the carriers in the bottom layer graphene while a top gate controls the top graphene layer, have been theoretically shown to exhibit negative differential resistance (NDR) in the tunneling characteristics, due to resonance in tunneling when the Dirac points of the two graphene layers are aligned. Britnell et al. first demonstrated gatecontrolled tunneling in exfoliated graphene – hexagonal boron nitride (h-BN) – graphene heterostructures and later demonstrated resonant tunneling induced NDR in a similar structure. It has also theoretically been shown that the resonance peak is largely dependent on the degree of defect-induced disorder and may also depend on the misorientation of the two graphene layers. Although an exfoliated graphene-based system allows the observation of NDR, the large scale realization of these devices is not possible. In this work, SymFETs with both graphene and h-BN grown by chemical vapor deposition (CVD) have been fabricated and characterized. Figure 1 shows the structure of a graphene – h-BN – graphene SymFET. CVD graphene obtained from ACS Material was transferred onto 90-nm-thick SiO2 on a silicon substrate using wet transfer techniques, and then annealed in forming gas. After patterning the graphene by