Magnitude of the current in 2D interlayer tunneling devices

Abstract

Abstract:Using the Bardeen tunneling method with first-principles wave functions, computations are made of the tunneling current in graphene / hexagonal-boron-nitride / graphene (G/h-BN/G) vertical structures. Detailed comparison with prior experimental results is made, focusing on the magnitude of the achievable tunnel current. With inclusion of the effects of translational and rotational misalignment of the graphene and the h-BN, predicted currents are found to be about 15 larger than experimental values. A reduction in this discrepancy, to a factor of 2.5, is achieved by utilizing a realistic size for the band gap of the h-BN, hence affecting the exponential decay constant for the tunneling.

Unveiling the tunneling phenomena in graphene–graphene homo-junctions for emerging device applications

“…In nutshell, the application of high bias voltage generates 2D electron gas (2DEG) and 2D hole gas (2DHG) systems in both interlayer channels and graphene layers [34] respectively as depicted in figure 11. At this point, it is well understood that the combined effects of both room temperature and low bias voltage application facilitates the electrons travel in plane, whereas conduction through other sheets via interlayer channels is possible only in high bias voltage range which is so called vertical tunneling [29][30][31]. The above observation can also be justified from resistance versus voltage (R versus V) graph depicted in figure 12(a).…”

“…In this situation, current is directly proportional to the number of electrons capable of tunneling between the valence band and conduction band of tunneling channel which is referred as direct tunneling (DT). It can be inferred that the tunnel current is a linear function of the bands overlapping which in turn, is a linear function of the bias voltage [31]. Physically, this can be interpreted as overlapping of Fermi circle of one Dirac cone with empty states of the other which enables the tunneling of electrons between them [30].…”

“…From the value of barrier height i.e. 4.96 eV, it implies that at a high voltage, owing to narrowing of barrier potential the charge carriers can easily cross vacuum level of individual graphene sheets and starts flowing through interlayer channels [31][32][33]. The current which is flowing through interlayer channels of graphene is termed as interlayer tunneling current.…”

“…It is clear from graph that there is a transition from one state to another, suggesting bistable characteristics. According to Feenstra et al [31] when graphene layers are misaligned having finite twist angle between them, then threshold voltage is shifted to ħv f q/e where q and v f are reciprocal lattice vector and Fermi velocity (~10 6 ms −1 ) respectively. Corresponding to calculated q values in section 3.2, threshold voltage lies between 4.6-6.01 V. The physical significance lies in the fact that misaligned graphene sheets create thickness modulated 2D homo-junction barrier in which threshold voltage for conduction can be tuned by varying twist angle [30] according to equation (1).…”

Bifurcation and orientation-dependence of corrugation of 2D hexagonal boron nitride on palladium

“…This angle-dependent nature of the corrugation is enabled by a delicate balance between the chemical bonding and registry at the hBN/Pd interface, which reveals -separatelythe presence of geometrically and electronically corrugated domains. We expect that a similar approach could be used to investigate orientation-dependent interactions in other substrate-supported 2D layers as well as in 2D layered vertical heterostructures [37].…”