High-density arrays of Germanium nanowire photoresistors

A comparative study of the photoresistive properties and dynamics of ordered, high-density arrays of germanium nanowire photoresistor arrays with different optically transparent electrodes such as ultrathin gold films and thin-doped indium tin oxide (ITO) layers is presented. Germanium nanowires, with mean diameters of 50 and 100 nm were synthesized in the pores of anodized aluminum oxide (AAO) membranes. The top surface of the AAO-nanowire membranes were coated with an optically transparent conductive ITO electrode or semitransparent Au coating to perform photoconductivity. All of the Ge nanowires incorporated within the AAO membranes demonstrated similar electrical conductivity after probing with C-AFM at 25 V. It was observed that ITO and semi-transparent Au act as effective electrodes for measuring the photoconductivities of Ge nanowire arrays. Improvements in contact resistance between the electrodes and the nanowires was achieved by mechanically polishing and chemically etching the membranes.