Effect of Stone-Wales defect on an armchair graphene nanoribbon-based photodetector

摘要

The effect of Stone-Wales (SW) defect on the performance of an armchair graphene nanoribbon (AGNR)-based photodetector is studied. To model the SW defect two new tight-binding (TB) parameters are proposed that provide results that are in good agreement with density functional theory calculations. SW defect is introduced in different locations in the channel of the AGNR detector and the photocurrent, quantum efficiency and responsivity of defected structures are calculated using TB approximation and non-equilibrium Green's function formalism. By inspecting the photo-generated hole density in different points of the channel, the way that photocurrent is affected by SW defect in different defected structures is investigated. Our results show that the photocurrent of AGNR photodetector varies with the number and position of SW defect in the channel. Among the defected structures highest quantum efficiency is observed in the structure in which the SW defect is located near the contact with a higher bias voltage. However, the quantum efficiency in all defected structures is lower than their perfect counterpart. Since the low ratio of the photocurrent to the dark current limits the performance of photodetectors, improving this ratio is of great importance. We show that the presence of SW defect in the channel of AGNR photodetector increases this ratio. It is observed that the ratio of photocurrent to the dark current in the double-defect structure in which two SW defects are located at two ends of the channel is 4.7 times larger than the perfect photodetector. Our results also show that by inserting SW defect in the channel of AGNR photodetector its photo-detection range can be tuned to higher energies.