Spin Dependent Resonant Electron Tunneling through Graphene Double and Triple Barrier Junctions*

We study spin-dependent electron transport properties of graphene double and triple barrier junctions via first-principles calculations. These 2D double barrier junctions consist of two graphene leads, two vacuum barriers, and a quantum well of zigzag graphene nanoribbon (ZGNR). Previous studies suggest that zigzag graphene edges are magnetic, which enables the spin-dependent electron transport investigated in our work. We observe resonant electron tunneling, and find that highly spin-polarized electric current can be obtained in such junctions. Furthermore, spin polarization of the electric current can be controlled by charge doping via gate voltage. When the vacuum barrier is replaced with monolayer boron nitride, non-resonant electron transmission increases since the barrier height decreases. We also tune the transport properties by changing the width of the quantum well and explore the properties of graphene triple barrier junctions. These double and triple barrier junctions may have potential application as a resonant tunneling diode in low dimensional electronics.