Strain-gated infrared photodetector based on helical graphene nanoribbon

Control of nanoscale architecture provides unique opportunities to develop novel devices with better performance. Here, we construct a helical architecture by rolling up a graphene nanoribbon. We find that the helical graphene nanoribbon (h-GNR) exhibits direct band gap, high carrier mobility, and efficient photon absorption under infrared illumination. In addition, the electronic structures and optical properties of h-GNR can be precisely tuned by external strains. The band gaps of h-GNRs are given approximately by ${E}_g\ensuremath{\propto}{t}₀\left|\ensuremath{\varepsilon}\right|$, where ${t}₀$ is the hopping constant and $\ensuremath{\varepsilon}$ is the applied strain. The performance of photoresponse in h-GNR is then evaluated by using density-functional theory combined with Keldysh nonequilibrium Green's functions. Under illumination, h-GNR systems exhibit high photoresponsivity in a broad wavelength range, spanning from 1550 nm to $5.90\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m}$. The predicated photoresponsibility and external quantum efficiency are up to 98 mA/W and 3.45%, respectively. Such outstanding optoelectronic merits combined with exceptional electronic properties make h-GNRs promising candidates for fabricating advanced appliances of infrared photodetectors. Our work may pave the way for designing next-generation devices for infrared light detecting and harvesting.