Preparation And Performance Study Of Na-doped P-type ZnO: Na_x Thin Films

With band gap of 3.37eV and exciton binding energy of 60meV, ZnO has attracted considerable attention as a promising material for optoelectronic devices, especially for ultraviolet light-emitting diodes, laser diodes. However, the reliability of applicable p-type ZnO remains to be a great difficulty, which mainly arises from strong self-compensation of intrinsic donor defects, deep acceptor levels and low solubility of acceptor dopants. Na-doped p-type ZnO has been reported theoretically and experimently, but the solubility of Na dopant, mechanism of p-type behavior and radiative emission efficiency were investigated less.In this work, Na-doped ZnO:Nax films with different Na content in a wide range were prepared on quartz substrates by pulsed laser deposition(PLD). Effect of Na doping content on structure, electrical and optical properties were investigated, and main results were showed as following:(1) X-ray diffraction results show that all ZnO:Nax(x≤5%) are wurtize,with the preferential oritentation of (002).The crystalline quality and surface morphology degenerates seriously when Na content is more than 5%.(2) Hall-test witnessed the conduction type conversion from native n-type to p-type with increased Na content, and stable p-type was achieved in ZnO:Na0.02. According to XPS results, we attribute the achievement of p-type behavior to the formation of Nazn acceptors.(3) All ZnO:Nax films show high transmittance in the visible region, the band gap shifting is related to the energy-gap shrinkage. Compared with undoped ZnO, non-degenerated and even enhanced near-band-gap emission intensity is detected in ZnO:Nax film, which means it's possible to achieve both p-type and high radiative eimissoin efficiency by Na doping.