Observation of negative differential conductance in nanoscale p-n junctions

Recently p-n junction characteristics in nanometer scale have been investigated in relation with photonics and electronics applications. In this paper, we report the experimental observation of negative differential conductance (NDC), the basic indication of tunneling, in nanoscale p-n junctions under forward bias condition. The NDC has been observed only at low temperatures, suggesting that tunneling is mediated by some states in the band gap, most likely by individual dopants with deeper energy levels compared to bulk. Furthermore, we also observed random telegraph signal (RTS) at low temperatures, which is ascribed to sudden changes of charge states of an individual dopant. These results illustrate the nature of individual dopants in nanoscalep-n junctions and their impact on device characteristics.