Ultrafast Photoresponse Using Axial n-ZnO/p-CuO Heterostructure Nanowires Array-Based Photodetectors

Photodetector (PD) based on axial n-ZnO/p-CuO heterostructure (HS) nanowires (NWs) array was fabricated on Si substrate by using glancing angle deposition (GLAD) technique. The field emission scanning electron microscope (FE-SEM) image shows the formation of a well-aligned and vertical NW structure. A typical high-resolution transmission electron microscope (HR-TEM) image confirms the formation of an axial HS NW consisting of ZnO NW at the top and CuO NW at the bottom. A twofold enhanced photo-absorption was observed for axial n-ZnO/p-CuO HS NW as compared to pristine ZnO NWs. Moreover, X-ray photoelectron spectroscopy (XPS) analysis prove that there is no deviation in electronic state after the formation of HS. The axial n-ZnO/p-CuO HS NW based PD exhibited a very high rectification ratio of 1200, low dark current ( ${I}_{d}$ ) of 0.09 nA and an ultrafast photoresponse with rise time and fall time of 0.49 and 0.11 ms, respectively.