Carrier tunneling, current instabilities, and negative differential conductivity in nanocrystalline silicon - Silicon dioxide superlattices

Low temperature measurements of differential conductivity in nanocrystalline Si - amorphous SiO₂ superlattices surprisingly reveal a clear double-peak structure associated with tunneling via levels of light and heavy holes. Numerical simulations show not only detailed agreement with the experiment but also predict that the studied system has no stable solutions for carrier concentration higher than 10¹⁷ cm^-3. According to this prediction, partial screening of the external electric field generates current instabilities and oscillations, and that is experimentally observed. The developed model also suggests that a more uniform electric field and stabilization of carrier transport at a higher level of carrier density can be achieved under transient carrier injection.