Effects of phonon scattering on the electron transport and photocurrent of graphene quantum dot structures

The nonequilibrium Green's function (NEGF) on the basis of unitary transformation is used to study the effects of phonon scattering on the electron transport and photocurrent of rectangular Armchair graphene quantum dots (GQD) in different lengths and widths. Applying the Landauer-Buttiker formalism, the electron current and photocurrent is calculated. The noninteracting Hamiltonian is interpreted as nearest neighbor tight-binding model, and electron-phonon interaction contribution to the earlier Hamiltonian is written using the Holstein model. The obtained results show that electron-phonon coupling has three major effects: (i) phonon-assisted and phonon-restricted effect on the electron transport and photocurrent, (ii) increasing the band gap in the absence of photon radiation, and (iii) increasing and decreasing the band gap in the presence of photon radiation.