SWCNT-Si photodetector with position-dependent photoresponse

We report the realization of a novel photodetector in which the photocurrent behavior changes accordingly to the position of the light spot above the substrate. Using the dry transfer printing method, a Single Walled Carbon Nanotubes (SWCNTs) film has been deposited on top of a properly modified n-type silicon substrate. A small portion of the silicon substrate (covered by a nominal 140 nm layer of $\mathrm{S}\mathrm{i}_{3}\mathrm{N}_{4}$) was etched with hydrofluoric acid to expose the pure n-type silicon. In this way, the deposition of the nanotubes above all the substrate allows the formation of two different junctions within the same device: one with an insulating interlayer and one without. The presence of these two junctions allows the device to show different photocurrent behavior depending on the position of the light spot.