Effect of oxygen partial pressure on conductivity type of MgZnO nanocrystalline thin films prepared by metal-organic chemical vapor deposition

The properties of the MgZnO nanocrystalline thin films deposited on c-Al2O3 substrates by metal-organic chemical vapor deposition (MOCVD) at various oxygen partial pressures (Po2) were thoroughly studied. It was found that the nanocrystalline films grown in the oxygen partial pressure range from 38 to 56 Pa were all c-axis oriented. From the atomic force microscope (AFM) images and photoluminescence (PL) spectra, we could also find that both the surface morphologies and the optical properties of the MgZnO nanocrystalline thin films depended on the oxygen partial pressure greatly. Hall effect measurements confirmed the conversion of conduction type of MgZnO under a certain range of oxygen partial pressure. With the increase of oxygen content, the crystallinity of MgZnO nanocrystalline thin films was degraded to polycrystalline and the p-type MgZnO was produced when the oxygen partial pressure was larger than 50 Pa. The hole concentration and mobility could reach to 9.71×1017 cm−3 and 2.44 cm2 V−1 s−1, and the resistivity was 2.87 Ω cm while the oxygen partial pressure was 56 Pa.