Sonochemical Synthesis of a Zinc Oxide Core–Shell Nanorod Radial p–n Homojunction Ultraviolet Photodetector

We report for the first time on the growth of a homogeneous radial p–n junction in the ZnO core–shell configuration with a p-doped ZnO nanoshell structure grown around a high-quality unintentionally n-doped ZnO nanorod using sonochemistry. The simultaneous decomposition of phosphorous (P), zinc (Zn), and oxygen (O) from their respective precursors during sonication allows for the successful incorporation of P atoms into the ZnO lattice. The as-formed p–n junction shows a rectifying current–voltage characteristic that is consistent with a p–n junction with a threshold voltage of 1.3 V and an ideality factor of 33. The concentration of doping was estimated to be N A = 6.7 × 10 17 cm –3 on the p side from the capacitance–voltage measurements. The fabricated radial p–n junction demonstrated a record optical responsivity of 9.64 A/W and a noise equivalent power of 0.573 pW/√Hz under ultraviolet illumination, which is the highest for ZnO p–n junction devices.