The synthesis and electrical characterization of Cu₂O/Al:ZnO radial p–n junction nanowire arrays

Vertically aligned large-area p-Cu₂O/n-AZO (Al-doped ZnO) radial heterojunction nanowire arrays were synthesized on silicon without using catalysts in thermal chemical vapor deposition followed by e-beam evaporation. Scanning electron microscopy and high-resolution transmission electron microscopy results show that poly-crystalline Cu₂O nano-shells with thicknesses around 10 nm conformably formed on the entire periphery of pre-grown Al:ZnO single-crystalline nanowires. The Al doping concentration in the Al:ZnO nanowires with diameters around 50 nm were determined to be around 1.19 at.% by electron energy loss spectroscopy. Room-temperature photoluminescence spectra show that the broad green bands of pristine ZnO nanowires were eliminated by capping with Cu₂O nano-shells. The current–voltage (I–V) measurements show that the p-Cu₂O/n-AZO nanodiodes have well-defined current rectifying behavior. This paper provides a simple method to fabricate superior p–n radial nanowire arrays for developing nano-pixel optoelectronic devices and solar cells.