Negative differential conductivity in the hopping transport model

The effect of negative differential conductivity (NDC) in the hopping transport mode is studied by computer simulations. NDC is an important effect in a class of memory devices. Understanding the origin of NDC is vital to modeling these devices. Based on analytical arguments, it has been suggested by Shklovskii et al. thatNDCcan arise in the hopping model due to geometrical traps. Our computer simulations have confirmed this result. Another possibility is that the NDC is caused by Coulomb interaction between the charge carriers. This has been reported for special configurations of sites by Shin et al. We show that the NDC effect due to Coulomb interaction is not sensitive to the exact configuration of sites, and that it can appear also when the sites are placed randomly.