Influence of Structure on Electronic Charge Transport in 3D Ge Nanowire Networks in an Alumina Matrix

We demonstrate formation of material consisting of three-dimensional Germanium nanowire network embedded in an insulating alumina matrix. A wide range of such nanowire networks is produced using a simple magnetron sputtering deposition process. We are able to vary the network parameters including its geometry as well as the length and width of the nanowires. The charge transport in these materials is shown to be related to the nanowire surface per unit volume of the material, α. For low values of α, transport is characterized by space charge limited conduction and a drift of carriers in the extended states with intermittent trapping-detrapping in the localized states. For large values of α, charge transport occurs through hopping between localized electronic states, similar to observations in disorder-dominated arrays of quantum dots. A crossover between these two mechanisms is observed for the intermediate values of α. Our results are understood in terms of an almost linear scaling of the characteristic trap energy with changes in the nanowire network parameters.