Modelling a nanowire grid for light-sensing applications

Abstract

Nanostructures hold promise as building blocks for a new generation of sensing devices because they could enhance detection and conversion of nonelectrical phenomena into electrical signals. In this paper, we discuss the possible use of a semiconductor (GaAs) nanowire grid as a light sensor. Based on the previously measured electrical properties of a single GaAs nanowire, we propose a model to determine the resistance of a structure consisting of many nanowires forming a grid with metallic contacts. Due to the fact that the proposed geometry is partially disordered, the total resistance of the structure is determined implementing the random resistor network (RRN) methodology in our simulation model. In order to reduce the error caused by condition number and the machine epsilon, the RRN model is improved by introducing additional conditions for solving the transfer matrix formulation precisely. The proposed complex nanowire geometry is analysed for different grid sizes varying the number of nanowires and contacts. According to the nanowire doping profile, we have defined the fraction of active segments (FoS) that is light-sensitive. Simulation results have shown that light sensitivity of a nanowire grid is enhanced with increasing number of active segments while a relative change in the active segment resistance has only a minor influence on the resistance of the complete structure. Finally, we have optimized nanowire grid dimensions with respect to the simulation results and practical limitations.