High-performance photodetectors and enhanced field-emission of CdS nanowire arrays on CdSe single-crystalline sheets

Vertically aligned nanowire arrays (NWAs) of semiconductor materials, combined with the merits of the large surface-to-volume ratio and low reflectance induced by light scattering and trapping, have attracted growing interests in the fabrication of high-performance optoelectronic nano-devices due to their exceptional geometrical structure and device architecture. However, an inexpensive synthesis of II-VI group semiconductor NWAs, e.g. CdS, CdSe NWAs, especially their heterostructures, is still a great challenge, and the devices (photodetector, field emitter, etc.) based on these NWA heterostructures have therefore been rarely studied. Here, we report a new method of synthesizing high-quality vertical CdS NWAs which heteroepitaxially grow on CdSe single-crystalline sheets (SCSs). The CdS NWA/CdSe SCS heterostructures as a whole are designed and fabricated into novel photodetectors via E-beam Lithography. The obtained photodetectors exhibit excellent performance with high photosensitivity, responsivity, and external quantum efficiency, alongside fast response speed, and wide range response spectrum. Additionally, field-emission data of these vertically tapered CdS NWAs on CdSe SCS show enhanced properties with low turn-on field, high enhancement factor, and good stability. The results indicate that the synthesized CdS NWA/CdSe SCS heterostructure is a good candidate for broadband (ultraviolet-visible) photodetectors and field-emitters.