Magnitude of the Current in Two-Dimensional Interlayer Tunneling Devices
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. For previous computational results obtained with an analytic theory, a discrepancy of about 10,000 between theory and experiment was obtained. With the first-principles method of the present work, this discrepancy is reduced to a factor of 300, through the use of realistic values for the wave function magnitudes and the exponential decay constant for the tunneling. Further reduction in the discrepancy, to a factor of 40, is achieved by including the effects of translational and rotational misalignment of the graphene and the h-BN. Possible origins for this remaining discrepancy between theory and experiment are discussed.