Controlling phosphorus doping concentration in ZnO nanorods by low temperature hydrothermal method

Phosphorous-doped ZnO nanorods (NRs) were synthesized with controllable morphology and doping concentration on top of the array of undoped natural n-type ZnO NRs by hydrothermal process. By changing the concentration of NH4OH to adjust the pH of the reactant solution containing zinc acetate, hexamethylenetetramine, and ammonium phosphate, it was possible to control the morphology, doping concentration, and band structure of the ZnO nanostructures formed on the top side of the undoped NRs array. When the NH4OH concentration was 1 vol% substitutional dopant P formed shallow acceptor levels in the ZnO NRs, while higher NH4OH concentration resulted in the formation of donor levels as well as the compensation of the acceptors. A model p-n homojunction device based on the P-doped ZnO NRs consecutively attached to the initially synthesized n-type NRs showed a rectifying junction behavior confirming the formation of the p-type ZnO NRs with low doping concentration of P.