Photoconductive response of strained silicon nanowires: A Monte Carlo study

Using Ensemble Monte Carlo simulations the photocurrent in a 500nm long strained [110] silicon nanowire with diameter of 3.1 nm is investigated. It was observed that a phototransistor based on this nanowire can have responsivities in the order of 21.3 mA/W for an input light wavelength of 532 nm and intensity of 0.25-2.5 kW/cm2. The super-unity slope of 1.2 in photo conductance versus input light intensity suggests that the nanowire has a photoconductive gain and highlights its advantage over germanium nanowires with sub-unity slope (0.77). The generated photocurrents are in the 0.1 nA-1 nA range. Density Functional Theory (DFT) and Tight Binding (TB) methods were used for strain application and band structure calculation, respectively. Both longitudinal acoustic and optical phonons were included in the calculation of the carrier-phonon scattering events, which showed a two-order of magnitude stronger role for longitudinal optical phonons.