Tuning the p-type conductivity of ZnSe nanowiresvia 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 [11 ] 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 × 1019 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 >107 and a small ideality factor of ∼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 ∼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.