Mechanism of p-type conductivity for phosphorus-doped ZnO thin film

Abstract

A p-type phosphorus-doped ZnO film (ZnO : P) was grown on a quartz substrate by sputtering a ZnO target mixed with 2 wt% P2O5 using a mixture of Ar and O2 and then annealed rapidly at 750 °C for 5 min in air ambient. The lattice constant of the c-axis was 0.5176 nm, smaller than the value of 0.5211 nm of pure ZnO, implying substitutional P at a Zn antisite (PZn). The binding energy of P2p1/3 is 133.5 eV, which is different from that of the P–O bond in P2O5 and of the P–Zn bond in Zn3P2, but close to that of P–O–P and P–O–Zn bonds in zinc phosphate glass mainly composed of ZnO and P2O5. The 80 K photoluminescence spectrum shows neutral acceptor bound exciton emission at 3.34 eV. Based on the above experimental results, it is suggested that P substitutes for a Zn antisite in the ZnO : P and forms an acceptor complex with two Zn vacancies, and the acceptor complex is responsible for p-type conductivity of ZnO : P.