A computational study of structural, electronic and carrier mobility of boron and phosphorus/nitrogen co-doped graphene

Opening a bandgap in graphene by doping with lighter elements plays a vital role in the next generation nanoelectronic devices. Here, we present the structural, electronic, and mobility of graphene co-doped with boron/nitrogen (BCN) and boron/phosphorus (BCP) using density functional theory with the inclusion of van der Waals interactions. By analyzing the band structure, it is found that BCP shows a direct bandgap whereas BCN exhibits an indirect bandgap. The bandgap values calculated using PBE (HSE) functional are (1.97 eV) (3.19 eV) for BCN and 0.55 eV (1.18 eV) for BCP. From phonon dispersion results, it is apparent that both BCN and BCP shows positive frequencies within the Brillouin zone demonstrating the lattice dynamical stability of these materials. Deformation potential theory is applied to calculate the electron/hole mobility by applying the uniaxial strain along x- and y-directions. It is seen that BCP possess significantly larger mobility compared to BCN. For BCP, the mobility of electron is 1588 (2999) and that of the hole is and 1607 (838) along x-direction (y-direction) in units of cm(2)V(-1)s(-1), respectively, which are larger than MoS2. Also, Boltzmann theory within the constant relaxation time approximation is used to determine the temperature dependent conductivity, and the results are consistent with the deformation theory.