Hydrogen incorporation effect in phosphorus-doped p-type ZnO thin films grown by radio-frequency magnetron sputtering

We report on the influence of hydrogen incorporation on the conductivity of phosphorous (P) doped ZnO thin films grown by using radio-frequency (RF) magnetron sputtering. The P dopant is an oxide form of P₂O₅, which is introduced into ZnO thin films using RF plasma with oxygen ambient to suppress the generation of O vacancies. The resultant P-doped ZnO thin films were analyzed by means of field-emission scanning electron microcopy (FE-SEM), atomic force microscopy (AFM), secondary ion mass spectroscopy (SIMS), Fourier transform infrared (FT-IR) spectroscopy, photoluminescence and Hall effect measurements. It was observed that the P₂O₅-doped ZnO thin films annealed at 800 °C exhibited the best electrical property with p-type behavior. Hydrogen atoms in ZnO thin films play an unusual role since it acts as a shallow donor and it may control the n-type conductivity in undoped material. Measurements revealed that the hydrogen atoms can be easily incorporated from the P-doped ZnO sputtering target as the natural hydrogen incorporation in P-doped ZnO thin films during magnetron sputtering. The role of hydrogen atoms incorporated in ZnO thin films is investigated by means of SIMS analysis.