Geometry-induced high performance ultraviolet photodetectors in kinked SnO2 nanowires

Abstract

SnO₂ nanowires have been widely utilized in photodetectors due to their large surface to volume ratio and semiconducting characteristics. In general, SnO₂-nanowire-based photodetectors exhibit high photocurrent but a slow response speed. Here we explored the important role of geometry in nanowire-based photodetectors, as exemplified by the study of the UV photodetector fabricated from a kinked single-crystal SnO₂ nanowire, in which two kinds of photodetectors, based on the straight and kinked SnO₂ nanowire, respectively, have been fabricated on the same SnO₂ nanowire for comparison. We found that both the photocurrent and response time of the SnO₂ nanowire were improved greatly by the kinked structure; the photoresponsivity and external quantum efficiency (EQE) are measured to be ultrahigh as 1.2 × 10⁷ A W⁻¹ and 6.0 × 10⁹%, respectively. Moreover, the photoresponse time exhibits a hundred times improvement, compared with the straight nanowire case. Such an improvement was attributed to the enhancement effect of the kinked structure to the local electric field, which benefits the electron–hole separation efficiency and the transmit time of carrier, thus improving both the photocurrent and response time of the SnO₂ nanowire. As the enhancement of the photodetector results from geometry exclusively, this simple strategy is promising to be extended to the applications of other low dimensional materials.