I. Introduction
Layered heterostructures of two dimensional (2D) materials have become a vast field of research with reports of interesting physical phenomena for a wide variety of potential applications [1]. One such application is the vertical interlayer tunneling, such as has been demonstrated for a stacked monolayer graphene - hexagonal boron nitride (hBN) - monolayer graphene heterostructure [2]. Application of a gate voltage enables one to modulate the interplay among the density of states and the electrostatic potentials in the two graphene layers, and thereby control the current flow between layers. However, the tunneling in [2] was non-resonant. If the band structures also can be aligned, then resulting resonant interlayer tunneling could be the basis for interlayer tunneling FETs (ITFETs) with negative differential resistance (NDR) [3]–[6]. Recently, it has been reported that NDR has been achieved through physical rotational alignment of two graphene layers that, in turn, aligns the Dirac cones at the corners (K-points) of the Brillouin zone [7]. Similarly, for bilayer graphene (BLG), rotational alignment of the parabolic band structures has been shown to produce substantial NDR [8]. Recent advances in fabrication of so-called Van der Waals heterostructures of layered 2D materials have made it possible to fabricate devices with clean heterointerfaces [9]. Utilizing such techniques, we have fabricated a stacked double BLG heterostructure with hBN used as the bottom dielectric, interlayer dielectric, and the top capping layer. We report here the results for this structure operating as a vertical ITFET device. We show multiple NDR peaks, consistent with the more complex band structure of BLG as compared to monolayer graphene. Through temperature-dependent and in-plane magneto-transport measurement, it is confirmed that the NDR is a result of resonant tunneling due to band alignment between layers. We also demonstrate that a one transistor static random access memory (SRAM) or latch can be realized using this NDR characteristic.