Lateral photovoltaic effect in the Fe$_3$O$_4$/SiO$_2$/$n$-Si structure: influence of the SiO$_2$ layer thickness

This work presents a study of the lateral photovoltaic effect in the Fe$_3$O$_4$/SiO$_2$/$n$-Si structure with a silicon oxide layer thickness of 2 and 5 nm. As it was shown an increase of the SiO$_2$ layer thickness in the investigated structure leads to a change in the behavior of the dependences of the photovoltaic sensitivity and nonlinearity on the Fe$_3$O$_4$ film thickness, as well as in the shape of the photoresponse signals under pulsed illumination. It was established that the change of the photosensitivity in the Fe$_3$O$_4$/SiO$_2$/$n$-Si structure with increasing SiO$_2$ layer thickness is due to both an influence of surface and interface states at the SiO$_2$/$n$-Si interface and a redistribution of conductivity in the double-channel system. The extrema presence in the thickness dependence of photovoltaic characteristics is associated with a quantum-size effect, which modulates the built-in barrier height.