Graphene in van der Waals heterostructures and transistors

Graphene tunnelling transistors are made by sandwiching a nanometre-thick barrier layer of hexagonal boron nitride (hBN) between two monolayer graphene electrodes.  The tunnel current is controlled by the bias voltage applied between the two graphene electrodes and by the gate voltage between the lower graphene layer and the doped Si layer of an SiO2/Si substrate.  When the crystalline lattices of the graphene layers are carefully aligned, electrons can tunnel with conservation of momentum, leading to a strong resonant peak in the current-voltage characteristics and associated negative differential conductance [1,2].  This talk will describe the physics of these devices including the chirality [3,4] of the tunnelling Dirac-Weyl fermions, and the effects of defect- and phonon-assisted tunnelling [5] on the device characteristics.  Our very recent work on the electronic properties of other types of van der Waals heterostructure transistors will also be reported.

[1]        A. Mishchenko et al.; Nature Nanotechnology 9, 808-813 (2014)

[2]        J. Gaskell et al.; Appl. Phys. Lett. 107, 103105 (2015)

[3]        M. T. Greenaway et al.; Nature Physics 11, 1057–1062 (2015)

[4]        J. R. Wallbank et al.; Science 353, 575-579 (2016)

[5]        E. E. Vdovin et al.; Phys. Rev. Lett. 116, 186603 (2016).

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