Abstract

We theoretically propose a bilayer graphene nanoribbon phototransistor (BGN-PT) based voltage-tunable terahertz/infrared (THz/IR) photodetector. The optical responsivity and quantum efficiency of our device, originated from interband transitions, are greater than those of GNR-PTs within the frequency range of THz to IR ($0<\hslash \omega <1\mathrm{eV}$). We reveal that the metallic armchair (Dirac) BGN-PTs have a maximum external quantum efficiency of about 40% at low energies of incident photons ($\hslash \omega \approx 0.4\mathrm{eV}$), which is robust across a wide range of relevant temperatures. The dependence of the optical characteristics on geometric parameters and bias voltages is studied as well. The photocurrent growth with gate and drain-source voltages, in the Dirac family, is larger than in the other two configurations. Also, we investigate the frequency shift of the lowest-energy peak and asymmetric electronic transitions with the potential difference between the gates. Our simulations indicate that the THz/FIR sensitivity and voltage tunability of $3p+2$ BGN-PTs are dramatically larger than in the other two families.

© 2016 Optical Society of America

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