Preparation And Investigation Of P-type ZnO Thin Film By Pulsed Laser Deposition

ZnO is an important direct wide band gap semiconductor (Eg～3.37 eV at 300 K), and has large exciton binding energy about 60 meV. Theoretically, it can realize stimulated ultraviolet emission at room temperature. ZnO is an excellent candidate for the fabrication of ultraviolet optoelectronic devices. However, the difficulty of preparing high quality p-type ZnO blocks the commercial application of ZnO-based optoelectronic device. The aim of this dissertation is researching and preparing p-type ZnO thin film by pulsed laser deposition. The major work and results are as follows:The four sets of ZnO thin film samples were deposited on c-plane sapphire substrate at different growth temperature. The sample deposited at 550℃exhibited the best crystal quality and optical property. So the growth temperature of 550℃is suitable for depositing ZnO thin film in our experiment.The effect of annealing temperature and growth temperature on the properties of the Sb-doped ZnO thin films were investigated with the aim of obtaining high-quality p-type ZnO thin films. The sample annealed at 950℃and grown at 550℃exhibited p-type conductivity. It gave a carrier concentration of 2.290×1017 cm-3 at room temperature. A strong acceptor-bound exciton (A0X) emission was observed in the low-temperature photoluminescence (PL) spectra. It was proved that the A0X emission is related to Sb doping.The ZnO:Sb thin films coated with AIN layer were annealed at nitrogen. PL spectra showed that the AIN layers could decrease the concentration of oxygen vacancies produced by anneal. Oxygen vacancy is a donor defect in ZnO. By deposited AIN layer on ZnO thin film, the oxygen vacancy concentration could be effectively controlled for realizing the p-type ZnO.The effect of growth temperature on the properties of the P-doped ZnO thin film was investigated. The samples deposited at the temperatures of 350℃and 450℃exhibited p-type conductivity; The p-type ZnO:P film deposited at 450℃showed a resistivity of 1.846 Ω·cm, a relatively high hole mobility of 6.63 cm2V-1s-1 at room temperature. The measurements of low-temperature PL spectra demonstrated that the samples deposited at the substrate temperatures of 350℃and 450℃showed a strong A0X emission. It was proved that the A0X emission is related to P doping.The effect of Ag doping on the optical properties of ZnO film was also investigated. The PL spectra at room temperature showed that the doping of Ag could decrease the oxygen vacancy in ZnO film deposited at low temperature such as 350℃and 450℃.