ZnO/c-Si heterojunction interface tuning by interlayers

The junction properties of isotype and anisotype n(+)-ZnO/c-Si heterostructures have been studied by electrical and photoelectrical methods. We present evidence that the junction properties are strongly affected by a 10-30 nm thick ZnO layer closest to the heterointerface with distinctively different properties than those of the ZnO film bulk. This layer supports a dominant current flow via multistep tunnelling-recombination. When a 10 nn thin ZnS or ZnSe interlayer is inserted charge transport is controlled by thermionic emission. The interlayer acts as spacer and increases the band bending in the silicon absorber. However, there is still a too high trap density at the interlayer/c-Si interface, so that V-oc does not exceed 0.25-0.32 V.