ZnSe nanowire/Si p-n heterojunctions: device construction and optoelectronic applications.

Nano-heterojunctions will play essential roles in future nano-electronic and nano-optoelectronic devices. However, their extensive applications are impeded by the complicated multi-step growth method involved and the requirements for precise nanowire (NW) positioning/alignment. Here, we develop a facile method to fabricate zinc selenide NW (ZnSeNW)/silicon p-n heterojunctions by transferring the p-type ZnSeNWs onto a SiO₂/Si substrate with pre-defined Si windows; the physical contact of the NWs with the Si substrate via van der Waals force leads to the formation of heterojunctions. Electrical measurements on the heterojunctions reveal their excellent diode characteristics with a relatively small ideality factor of ∼1.95, high rectification ratio of ∼10⁶, and low turn-on voltage of ∼0.9 V. Moreover, heterojunction field-effect transistors are constructed based on the p-ZnSeNWs and show remarkable performance enhancement compared to the device counterparts with a metal-oxide-semiconductor field-effect transistor structure. The enhanced gate coupling between the NW conduction channel and the heterojunction gate is believed to be responsible for the high device performance. Significantly, under AM 1.5G light illumination, the heterojunctions exhibit pronounced photovoltaic behavior, yielding a power conversion efficiency of ∼1.8%. Our results demonstrate the great potential of ZnSeNW/Si p-n heterojunctions in high-performance nano-device applications.