Mapping the structural, electrical, and optical properties of hydrothermally grown phosphorus-doped ZnO nanorods for optoelectronic device applications

The phosphorus-doped ZnO nanorods were prepared using hydrothermal process, whose structural modifications as a function of doping concentration were investigated using X-ray diffraction. The dopant concentration-dependent enhancement in length and diameter of the nanorods had established the phosphorus doping in ZnO nanorods. The gradual transformation in the type of conductivity as observed from the variation of carrier concentration and Hall coefficient had further confirmed the phosphorus doping. The modification of carrier concentration in the ZnO nanorods due to phosphorus doping was understood on the basis of the amphoteric nature of the phosphorus. The ZnO nanorods in the absence of phosphorus showed the photoluminescence (PL) in the range of the ultraviolet (UV) and visible regimes. The UV emission, i.e. near-band-edge emission of ZnO, was found to be red-shifted after the doping of phosphorus, which was attributed to donor-acceptor pair formation. The observed emissions in the visible regime were due to the deep level emissions that were aroused from various defects in ZnO. The Al-doped ZnO seed layer was found to be responsible for the observed near-infrared (NIR) emission. The PL emission in UV and visible regimes can cover a wide range of applications from biological to optoelectronic devices.