Tailoring the photovoltaic effect in (1 1 1) oriented BiFeO₃/LaFeO₃ superlattices

Ferroelectric and photovoltaic properties of (BiFeO₃)_(1-x)Λ/(LaFeO₃) _xΛ superlattices grown by pulsed laser deposition have been investigated (Λ being the bilayer thickness). For a high concentration of BiFeO₃ a ferroelectric state is observed simultaneously with a switchable photovoltaic response. In contrast for certain concentration of LaFeO₃ a non-switchable photovoltaic effect is evidenced. Such modulation of the PV response in the superlattices is attributed to the ferroelectric to paraelectric phase transition which is controlled with the increase of x. Remarkably, concomitant to this change of PV mechanism, a change of the conduction mechanism also seems to take place from a bulk-limited to an interface-limited transport as x increases.