Tuning the p-type conductivity of ZnSe nanowires via silver doping for rectifying and photovoltaic device applications

Applications of one-dimensional (1D) semiconductor nanostructures in nanoelectronics and nano-optoelectronics rely on the ability to rationally tune their electrical transport properties. Here we report the synthesis of single-crystalline Ag-doped ZnSe nanowires (NWs) by using silver sulfide (Ag2S) as the p-type dopant via a thermal evaporation method. The ZnSe: Ag NWs had the zinc blende structure with [111] growth orientation. Significantly, the conductivities of the NWs could be tuned over 9 orders of magnitude by adjusting the Ag doping levels. Field-effect transistors (FETs) constructed from the ZnSe: Ag NWs verified their p-type nature with a hole concentration of up to 2.1 x 10(19) cm(-3), which is the highest value achieved for p-type ZnSe nanostructures thus far. Schottky barrier diodes (SBDs) based on the ZnSe: Ag NW/ITO junctions exhibited remarkable rectifying behavior, with a rectification ratio of > 10(7) and a small ideality factor of similar to 1.29 at 320 K. Moreover, photovoltaic devices were fabricated from the ZnSe NW array/Si p-n heterojunctions by aligning the p-ZnSe NWs in a parallel fashion on a n-Si substrate. The device with a graphene top electrode showed a large fill factor (FF) of 61%, yielding a power conversion efficiency of similar to 1.04%. The realization of p-type ZnSe NWs with tunable conductivity opens up opportunities for a host of high-performance nanoelectronic and nano-optoelectronic devices.