Fabrication of carbon nanotube/silicon nanowire array heterojunctions and their silicon nanowire length dependent photoresponses

► Heterojunction structures were fabricated, which consisted of a double-walled carbon nanotube (DWCNT) thin film coated either on an n-type silicon wafer or an n-type silicon nanowires (SiNW) array with varied lengths. ► It is for the first time for investigating the effect of SiNW length on the photoresponse of the DWCNT/SiNW heterojunction photoconductive devices without redox electrolyte. Such research is quite important for applications of SiNWs array-based devices in photodetectors and optical switches. ► The photoresponse was revealed to dramatically depend on the length of silicon nanowires in the heterojunctions. Increase in the length of SiNWs led first to increase and then to decrease of photoresponse of the heterojunctions, and a maximum photoresponse value of 10.72 was measured for the heterojunction consisting of SiNWs of 600 nm. The heterojunction also showed fast photocurrent response (<10 ms), good reproducibility and stability. The current results suggest that the DWCNTs/SiNWs array heterojunctions have potential application in photodetectors and optical switches.