Limits for the graphene on ferroelectric domain wall p-n-junction   rectifier for different regimes of current
  Here we present the theory of the conductivity of pn junction (pnJ) in graphene channel, placed on ferroelectric substrate, caused by ferroelectric domain wall (FDW) for the case of arbitrary current regime: from ballistic to diffusive one. We calculated the ratio of the pnJ conductions for opposite polarities of voltages, applied to source and drain electrodes of the channel,G+/G- as the function of the graphene channel length L, electron mean free path {\lambda} and ferroelectric substrate permittivity. We have demonstrated, that the small values of G+/G-(0.1 and smaller), which correspond to efficient graphene pnJ based rectifier, can be obtained for the ferroelectrics with high and for the ratios of L/{\lambda}~1 or smaller. However, for ferroelectrics with extremely high permittivity(relaxor or PbZrxTi1-xO3 with composition x near the morphotropic phase boundary x=0.52) the ratio G+/G- can be essentially smaller then unity for the case of a pronounced diffusive regime of current as well. This makes the ferroelectric substrates with high permittivity excellent candidates for the fabrication of new generation of rectifiers based on the graphene pnJ. Temperature effect on ratio was studied within Landau-Ginzburg-Devonshire approach. We have demonstrated that rectifying properties of the graphene pnJ become better in the vicinity of Curie temperature. However, for the temperatures higher than Curie temperature the rectifying effect vanishes due to the ferroelectric polarization disappearance. 
Maksym V. Strikha and Anna N. Morozovska
cond-mat.mtrl-sci cond-mat.mes-hall