Impact of film thickness on the external quantum efficiency of bulk photovoltaic effects in Mn-doped BiFeO3 thin films

This work demonstrates an enhancement of the external quantum efficiency (eta (ex)) associated with the bulk photovoltaic effect (BPVE) resulting from the ballistic conduction of hot carriers in indium tin oxide/Mn-doped BiFeO3 (BFMO)/SrRuO3 capacitors in response to a blue-violet laser (lambda = 405 nm). The effect of the BFMO film thickness on the short circuit current showed an abnormal trend in the case of films less than 100 nm thick. This result established that ballistic conduction was the dominant BPVE mechanism, although an effect of the BFMO/electrode interface on the photovoltaic properties may also have been a factor. BFMO films with thicknesses less than 100 nm also exhibited enhanced external quantum efficiency, demonstrating that the ballistic conduction of hot carriers enhanced eta (ex).