Bilayer armchair graphene nanoribbon photodetector with Stone-Wales defect: A computational study

Abstract

Bilayer armchair graphene nanoribbons (BAGNRs), due to their low sensitivity to low frequency noise and high controllability of their bandgap have drawn a lot of attention as building blocks of photodetectors in recent years. In this work, using tight binding (TB) method and non-equilibrium Green's function formalism (NEGF) a computational study has been done on the BAGNR photodetector with perfect and Stone-Wales (SW) defected channel and the effect of defects' number and position on the device performance has been investigated. In order to validate the TB parameters used in this work, the bandstructures of both perfect and SW defected BAGNRs are compared with the results of DFT method and a good matching is obtained. Simulation results show that perfect BAGNR photodetector has quantum efficiency (QE) of 19.77% at 0.12 eV photon energy. Among defected photodetectors, highest QE of 21.77% belongs to the structure with single SW defect near the right contact (higher bias voltage) at 0.14 eV. This structure also possesses the highest Iph/Idark of 64.45 which is 1.8 times larger than Iph/Idark of perfect BAGNR photodetector. Moreover, the structure with two SW defects located at left and right sides of the channel exhibits a drastically low Idark which results in a high Iph/Idark. In addition, this structure yields the high QE (19.72%) at blue-shifted photon energy of 0.2 eV which makes it a suitable choice for mid-wavelength infrared applications.